Absorbent articles with improved cores

ABSTRACT

Absorbent articles and absorbent core structures with improved core strength and stability with long core end seal and channel hang times.

FIELD OF THE INVENTION

The present invention generally relates to an absorbent core for use inan absorbent article, and more particularly to an absorbent core withabsorbent particulate polymer material.

BACKGROUND OF THE INVENTION

Disposable absorbent articles for receiving and retaining bodilydischarges such as urine or feces are generally known in the art.Examples of these include disposable diapers, training pants and adultincontinence articles. Typically, disposable diapers comprise a liquidpervious topsheet that faces the wearer's body, a liquid imperviousbacksheet that faces the wearer's clothing and an absorbent coreinterposed between the liquid pervious topsheet and the backsheet.

Since their introduction into the market place, disposable diapers havecontinued to improve regarding comfort, fit and functionalities.

An important component of disposable absorbent articles is the absorbentcore structure. The absorbent core structure typically includesabsorbent polymer material, such as hydrogel-forming polymer material,also referred to as absorbent gelling material, AGM, or super-absorbentpolymer, SAP. This absorbent polymer material ensures that large amountsof bodily fluids, e.g. urine, can be absorbed by the absorbent articleduring its use and be locked away, thus providing low rewet and goodskin dryness.

Traditionally, the absorbent polymer material is incorporated into theabsorbent core structure with cellulose or cellulosic fibres. However,over the past years, significant effort has been spent to make thinnerabsorbent core structures which can still acquire and store largequantities of discharged body fluids, in particular urine. Hereto, ithas been proposed to reduce or eliminate these cellulose fibres from theabsorbent core structures. To maintain the mechanical stability of theabsorbent core structures, small quantities of a fiberized net structuremay be added to stabilize the absorbent polymer material. To reducestiffness in the absorbent core, the core may also comprise channels,areas substantially free of absorbent polymer particles or absorbentpolymer material. The channels provide improved liquid transport, andhence faster acquisition, and more efficient liquid absorbency over thewhole absorbent structure.

One consequence of thinner and denser core structures and channels isthat the reduced void volume results in higher total expansion of theabsorbent core with the consequence that the forces exerted on the coreseals upon swelling of the absorbent cores are increased compared toconventional absorbent cores. Thus, there is a need to improve the bondstrength of the core end seals and the channel seals. Additionally,there is a need for core adhesives and materials that can form fiberizednet structures that can promote the stability of the absorbent polymermaterial, such as through formation of a less dense net structure, whilestill providing strength.

Accordingly, there is a need to improve the bond strength of the coreand channel seals, and to provide greater stability of the coreintegrity.

SUMMARY OF THE INVENTION

An absorbent core extending in a lateral direction and a longitudinaldirection, the absorbent core having a front edge, a back edge, and twoside edges, the absorbent core comprising:

a first substrate and a second substrate, wherein each substratecomprises an inner surface and an outer surface,

an absorbent material comprising an absorbent particulate polymerdisposed between the first substrate and the second substrate in anabsorbent particulate polymer material area, the absorbent particulatepolymer material area encompassing one or more channel area(s) that aresubstantially free of absorbent material,

a hot melt adhesive applied directly to the inner surface of at leastone of the first or second substrate, wherein the adhesive bonds theinner surface of the first substrate to the inner surface of the secondsubstrate through the one or more channel area(s) substantially free ofabsorbent material; and

wherein the bond of the inner surface of the first substrate to theinner surface of the second substrate through the one or more channelarea(s) substantially free of absorbent material has a normalizedinitial channel hang time of at least about 70 minutes and a normalizedfinal channel hang time of at least about 800 minutes.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a diaper in accordance with an embodiment ofthe present invention.

FIG. 2 is a cross sectional view of the diaper shown in FIG. 1 takenalong the sectional line 2-2 of FIG. 1.

FIG. 3 is a partial cross sectional view of an absorbent core layer inaccordance with an embodiment of this invention.

FIG. 4 is a partial cross sectional view of an absorbent core layer inaccordance with another embodiment of this invention.

FIG. 5 is a plan view of the absorbent core layer illustrated in FIG. 3.

FIG. 6 is a plan view of a second absorbent core layer in accordancewith an embodiment of this invention.

FIG. 7a is a partial sectional view of an absorbent core comprising acombination of the first and second absorbent core layers illustrated inFIGS. 5 and 6.

FIG. 7b is a partial sectional view of an absorbent core comprising acombination of the first and second absorbent core layers illustrated inFIGS. 5 and 6.

FIG. 8 is a plan view of the absorbent core illustrated in FIGS. 7a and7 b.

FIG. 9 shows a perspective view of an absorbent structure.

FIG. 10 shows a cross sectional view of an alternative absorbent core.

FIG. 11 is a schematic illustration of a process for making an absorbentcore in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION Definitions

“Absorbent article” refers to devices that absorb and contain bodyexudates, and, more specifically, refers to devices that are placedagainst or in proximity to the body of the wearer to absorb and containthe various exudates discharged from the body. Absorbent articles mayinclude diapers, training pants, adult incontinence undergarments,feminine hygiene products, breast pads, care mats, bibs, wound dressingproducts, and the like. As used herein, the term “body fluids” or “bodyexudates” includes, but is not limited to, urine, blood, vaginaldischarges, breast milk, sweat and fecal matter.

“Absorbent core” or “absorbent structure” means a structure typicallydisposed between a topsheet and backsheet of an absorbent article forabsorbing and containing liquid received by the absorbent article andmay comprise one or more substrates, absorbent polymer material disposedon the one or more substrates, and a thermoplastic composition on theabsorbent particulate polymer material and at least a portion of the oneor more substrates for immobilizing the absorbent particulate polymermaterial on the one or more substrates. In a multilayer absorbent core,the absorbent core may also include a cover layer. The one or moresubstrates and the cover layer may comprise a nonwoven. Further, theabsorbent core may be substantially cellulose free. The absorbent coredoes not include an acquisition system, a topsheet, or a backsheet ofthe absorbent article. In a certain embodiment, the absorbent core mayconsist essentially of the one or more substrates, the absorbent polymermaterial, the fiberized net structure, and optionally the cover layer.

“Absorbent polymer material,” “absorbent gelling material,” “AGM,”“superabsorbent,” “superabsorbent polymer material”, and “superabsorbentmaterial” are used herein interchangeably and refer to cross linkedpolymeric materials that can absorb at least 5 times their weight of anaqueous 0.9% saline solution as measured using the Centrifuge RetentionCapacity test (Edana 441.2-01).

“Absorbent particulate polymer material” is used herein to refer to anabsorbent polymer material which is in particulate form so as to beflowable in the dry state.

“Absorbent particulate polymer material area”, “superabsorbent polymermaterial area” or “absorbent material deposition area” as used hereinrefers to the area of the core wherein the first substrate and secondsubstrate are separated by a multiplicity of superabsorbent particles.In FIG. 8, the boundary of the absorbent particulate polymer materialarea is defined by the perimeter of the overlapping circles. There maybe some extraneous superabsorbent particles outside of this perimeterbetween the first substrate and second substrate.

“Airfelt” is used herein to refer to comminuted wood pulp, which is aform of cellulosic fiber.

“Comprise,” “comprising,” and “comprises” are open ended terms, eachspecifies the presence of what follows, e.g., a component, but does notpreclude the presence of other features, e.g., elements, steps,components known in the art, or disclosed herein.

“Consisting essentially of” is used herein to limit the scope of subjectmatter, such as that in a claim, to the specified materials or steps andthose that do not materially affect the basic and novel characteristicsof the subject matter.

“Disposable” is used in its ordinary sense to mean an article that isdisposed or discarded after a limited number of usage events overvarying lengths of time, for example, less than about 20 events, lessthan about 10 events, less than about 5 events, or less than about 2events.

“Diaper” refers to an absorbent article generally worn by infants andincontinent persons about the lower torso so as to encircle the waistand legs of the wearer and that is specifically adapted to receive andcontain urinary and fecal waste. As used herein, term “diaper” alsoincludes “pants” which is defined below.

“Fiber” and “filament” are used interchangeably.

“Fiberized net structure” as used herein is understood to comprise apolymer composition from which strands or a net structure is formed andapplied to the superabsorbent material with the intent to immobilize thesuperabsorbent material in both the dry and wet state. The fiberized netstructure of the present invention forms a fibrous network over thesuperabsorbent material.

A “nonwoven” is a manufactured sheet, web or batt of directionally orrandomly orientated fibers, bonded by friction, and/or cohesion and/oradhesion, excluding paper and products which are woven, knitted, tufted,stitch-bonded incorporating binding yarns or filaments, or felted bywet-milling, whether or not additionally needled. The fibers may be ofnatural or man-made origin and may be staple or continuous filaments orbe formed in situ. Commercially available fibers have diameters rangingfrom less than about 0.001 mm to more than about 0.2 mm and they come inseveral different forms: short fibers (known as staple, or chopped),continuous single fibers (filaments or monofilaments), untwisted bundlesof continuous filaments (tow), and twisted bundles of continuousfilaments (yarn). Nonwoven fabrics can be formed by many processes suchas meltblowing, spunbonding, solvent spinning, electrospinning, andcarding. The basis weight of nonwoven fabrics is usually expressed ingrams per square meter (gsm).

“Pant” or “training pant”, as used herein, refer to disposable garmentshaving a waist opening and leg openings designed for infant or adultwearers. A pant may be placed in position on the wearer by inserting thewearer's legs into the leg openings and sliding the pant into positionabout a wearer's lower torso. A pant may be preformed by any suitabletechnique including, but not limited to, joining together portions ofthe article using refastenable and/or non-refastenable bonds (e.g.,seam, weld, adhesive, cohesive bond, fastener, etc.). A pant may bepreformed anywhere along the circumference of the article (e.g., sidefastened, front waist fastened). While the terms “pant” or “pants” areused herein, pants are also commonly referred to as “closed diapers,”“prefastened diapers,” “pull-on diapers,” “training pants,” and“diaper-pants”. Suitable pants are disclosed in U.S. Pat. No. 5,246,433,issued to Hasse, et al. on Sep. 21, 1993; U.S. Pat. No. 5,569,234,issued to Buell et al. on Oct. 29, 1996; U.S. Pat. No. 6,120,487, issuedto Ashton on Sep. 19, 2000; U.S. Pat. No. 6,120,489, issued to Johnsonet al. on Sep. 19, 2000; U.S. Pat. No. 4,940,464, issued to Van Gompelet al. on Jul. 10, 1990; U.S. Pat. No. 5,092,861, issued to Nomura etal. on Mar. 3, 1992; U.S. Patent Publication No. 2003/0233082 A1,entitled “Highly Flexible And Low Deformation Fastening Device”, filedon Jun. 13, 2002; U.S. Pat. No. 5,897,545, issued to Kline et al. onApr. 27, 1999; U.S. Pat. No. 5,957,908, issued to Kline et al on Sep.28, 1999.

As used herein, the term “substantially” means generally the same oruniform but allowing for or having minor fluctuations from a definedproperty, definition, etc. For example, small measurable or immeasurablefluctuations in a measured property described herein, such as viscosity,melting point, etc. may result from human error or methodologyprecision. Other fluctuations are caused by inherent variations in themanufacturing process, thermal history of a formulation, and the like.The compositions of the present invention, nonetheless, would be said tobe substantially having the property as reported.

“Substantially cellulose free” is used herein to describe an article,such as an absorbent core, that contains less than 10% by weightcellulosic fibers, less than 5% cellulosic fibers, less than 1%cellulosic fibers, no cellulosic fibers, or no more than an immaterialamount of cellulosic fibers. An immaterial amount of cellulosic materialwould not materially affect the thinness, flexibility, or absorbency ofan absorbent core.

As used herein, the term “substrate” means any item having at least apartially or fully solidified fiber or planar surface. In some cases, asingle substrate may be positioned in a way that it is referred to astwo or more substrates; for example a folded film or folded non-woven,or two sides of a cardboard sheet folded over, wherein the two sides areadhesively bonded together. The substrates can be impermeable,permeable, porous or nonporous. In some cases, a substrate may bereferred to as a supporting sheet.

Article

FIG. 1 is a plan view of an article, such as a diaper, 10 according to acertain embodiment of the present invention. The diaper 10 is shown inits flat out, uncontracted state (i.e., without elastic inducedcontraction) and portions of the diaper 10 are cut away to more clearlyshow the underlying structure of the diaper 10. A portion of the diaper10 that contacts a wearer is facing the viewer in FIG. 1. The diaper 10generally may comprise a chassis 12 and an absorbent core 14 disposed inthe chassis.

The chassis 12 of the diaper 10 in FIG. 1 may comprise the main body ofthe diaper 10. The chassis 12 may comprise an outer covering 16including a topsheet 18, which may be liquid pervious, and/or abacksheet 20, which may be liquid impervious. The absorbent core 14 maybe encased between the topsheet 18 and the backsheet 20. The chassis 12may also include side panels 22, elasticized leg cuffs 24, and anelastic waist feature 26.

The leg cuffs 24 and the elastic waist feature 26 may each typicallycomprise elastic members 28. One end portion of the diaper 10 may beconfigured as a first waist of the diaper 10. An opposite end portion ofthe diaper 10 may be configured as a second waist region 32 of thediaper 10. An intermediate portion of the diaper 10 may be configured asa crotch region 34, which extends longitudinally between the first andsecond waist regions 30 and 32. The waist regions 30 and 32 may includeelastic elements such that they gather about the waist of the wearer toprovide improved fit and containment (elastic waist feature 26). Thecrotch region 34 is that portion of the diaper 10 which, when the diaper10 is worn, is generally positioned between the wearer's legs.

The diaper 10 is depicted in FIG. 1 with its longitudinal axis 36 andits transverse axis 38. The periphery 40 of the diaper 10 is defined bythe outer edges of the diaper 10 in which the longitudinal edges 42 rungenerally parallel to the longitudinal axis 36 of the diaper 10 and theend edges 44 run between the longitudinal edges 42 generally parallel tothe transverse axis 38 of the diaper 10. The chassis 12 may alsocomprise a fastening system, which may include at least one fasteningmember 46 and at least one stored landing zone 48.

The diaper 10 may also include such other features as are known in theart including front and rear ear panels, waist cap features, elasticsand the like to provide better fit, containment and aestheticcharacteristics. Such additional features are well known in the art andare e.g., described in U.S. Pat. Nos. 3,860,003 and 5,151,092.

In order to keep the diaper 10 in place about the wearer, at least aportion of the first waist region 30 may be attached by the fasteningmember 46 to at least a portion of the second waist region 32 to formleg opening(s) and an article waist. When fastened, the fastening systemcarries a tensile load around the article waist. The fastening systemmay allow an article user to hold one element of the fastening system,such as the fastening member 46, and connect the first waist region 30to the second waist region 32 in at least two places. This may beachieved through manipulation of bond strengths between the fasteningdevice elements.

According to certain embodiments, the diaper 10 may be provided with are-closable fastening system or may alternatively be provided in theform of a pant-type diaper. When the absorbent article is a diaper, itmay comprise a re-closable fastening system joined to the chassis forsecuring the diaper to a wearer. When the absorbent article is apant-type diaper, the article may comprise at least two side panelsjoined to the chassis and to each other to form a pant. The fasteningsystem and any component thereof may include any material suitable forsuch a use, including but not limited to plastics, films, foams,nonwoven, woven, paper, laminates, fiber reinforced plastics and thelike, or combinations thereof. In certain embodiments, the materialsmaking up the fastening device may be flexible. The flexibility mayallow the fastening system to conform to the shape of the body and thus,reduce the likelihood that the fastening system will irritate or injurethe wearer's skin.

For unitary absorbent articles, the chassis 12 and absorbent core 14 mayform the main structure of the diaper 10 with other features added toform the composite diaper structure. While the topsheet 18, thebacksheet 20, and the absorbent core 14 may be assembled in a variety ofwell-known configurations, preferred diaper configurations are describedgenerally in U.S. Pat. No. 5,554,145 entitled “Absorbent Article WithMultiple Zone Structural Elastic-Like Film Web Extensible Waist Feature”issued to Roe et al. on Sep. 10, 1996; U.S. Pat. No. 5,569,234 entitled“Disposable Pull-On Pant” issued to Buell et al. on Oct. 29, 1996; andU.S. Pat. No. 6,004,306 entitled “Absorbent Article WithMulti-Directional Extensible Side Panels” issued to Robles et al. onDec. 21, 1999.

The topsheet 18 in FIG. 1 may be fully or partially elasticized or maybe foreshortened to provide a void space between the topsheet 18 and theabsorbent core 14. Exemplary structures including elasticized orforeshortened topsheets are described in more detail in U.S. Pat. Nos.5,037,416 and 5,269,775.

The topsheet may be compliant, soft feeling, and non-irritating to thewearer's skin and may be elastically stretchable in one or moredirections. Further, the topsheet may be liquid pervious, permittingliquids (e.g., menses, urine, and/or runny feces) to penetrate throughits thickness. Various topsheets may also comprise a hydrophilicmaterial, for example, which is configured to draw bodily fluids into anabsorbent core of the chassis when these fluids are expelled from thebody. A suitable topsheet may be manufactured from a wide range ofmaterials, such as woven and nonwoven materials, apertured orhydroformed thermoplastic films, apertured nonwovens, porous foams,reticulated foams, reticulated thermoplastic films, and/or thermoplasticscrims, for example. Suitable apertured films may comprise thosedescribed in U.S. Pat. Nos. 3,929,135, 4,324,246, 4,342,314, 4,463,045,5,006,394, 5,628,097, 5,916,661, 6,545,197, and 6,107,539.

Apertured film or nonwoven topsheets typically may be pervious to bodilyexudates, yet non-absorbent, and have a reduced tendency to allow fluidsto pass back through and rewet the wearer's skin. Suitable woven andnonwoven materials may comprise natural fibers, such as, for example,wood or cotton fibers, synthetic fibers, such as, for example,polyester, polypropylene, or polyethylene fibers, or combinationsthereof. If the topsheet comprises fibers, the fibers may be spunbond,carded, wet-laid, meltblown, hydroentangled, or otherwise processed, forexample, as is generally known in the art.

The topsheet may comprise a skin care lotion. Examples of suitablelotions include, but are not limited to, those described in U.S. Pat.Nos. 5,607,760; 5,609,587; 5,635,191; 5,643,588; and 5,968,025, and asdescribed in U.S. Application No. 61/391,353, and as described in U.S.Pub. No. 2014-0257216. Beyond these compositions, the absorbent articlemay comprise soluble cyclodextrin derivatives such as those described inU.S. Pub. No. 2014/0274870.

Additionally, the topsheet of the present disclosure may be a tuftedlaminate web as disclosed in U.S. Pat. No. 7,410,683, and/or may be anapertured web as disclosed in PCT/CN2014/083769 having an internationalfiling date of Aug. 6, 2014.

In one embodiment, the topsheet may comprise graphics such that depthperception is created as described in U.S. Pat. No. 7,163,528. In otherembodiments, the topsheet may be an integrated acquisition layer andtopsheet as described in U.S. Ser. Nos. 14/680,426 or 14/634,928.

In one embodiment, the absorbent article may comprise a backsheet. Thebacksheet may be impervious, or at least partially impervious, to fluidsor body exudates (e.g., menses, urine, and/or runny feces) and may bemanufactured from a thin plastic film, although other flexible liquidimpervious materials may also be used. The backsheet may prevent thebody exudates or fluids absorbed and contained in an absorbent core ofthe absorbent article from wetting articles which contact the absorbentarticle, such as bedsheets, pajamas, clothes, and/or undergarments. Thebacksheet may comprise a woven or nonwoven material, polymeric filmssuch as thermoplastic films of polyethylene or polypropylene, and/or amulti-layer or composite materials comprising a film and a nonwovenmaterial (e.g., having an inner film layer and an outer nonwoven layer).A suitable backsheet may comprise a polyethylene film having a thicknessof from about 0.012 mm (0.5 mils) to about 0.051 mm (2.0 mils). Examplesof polyethylene films are manufactured by Clopay Corporation ofCincinnati, Ohio, under the designation BR-120 and BR-121, and byTredegar Film Products of Terre Haute, Ind., under the designationXP-39385.

One suitable material for the backsheet can be a liquid imperviousthermoplastic film having a thickness of from about 0.012 mm (0.50 mil)to about 0.051 mm (2.0 mils), for example including polyethylene orpolypropylene. Typically, the backsheet can have a basis weight of fromabout 5 g/m2 to about 35 g/m2. The backsheet can be typically positionedadjacent the outer-facing surface of the absorbent core and can bejoined thereto. For example, the backsheet may be secured to theabsorbent core by a uniform continuous layer of adhesive, a patternedlayer of adhesive, or an array of separate lines, spirals, or spots ofadhesive. Illustrative, but non-limiting adhesives, include adhesivesmanufactured by H. B. Fuller Company of St. Paul, Minn., U.S.A., andmarketed as HL-1358J. An example of a suitable attachment deviceincluding an open pattern network of filaments of adhesive is disclosedin U.S. Pat. No. 4,573,986. Another suitable attachment device includingseveral lines of adhesive filaments swirled into a spiral pattern isillustrated by the apparatus and methods shown in U.S. Pat. Nos.3,911,173; 4,785,996; and 4,842,666. Alternatively, the attachmentdevice may include heat bonds, pressure bonds, ultrasonic bonds, dynamicmechanical bonds, or any other suitable attachment device orcombinations of these attachment devices.

In one embodiment, the backsheet may be embossed and/or matte-finishedto provide a more cloth-like appearance. Further, the backsheet maypermit vapors to escape from the absorbent core of the absorbent article(i.e., the backsheet is breathable) while still preventing, or at leastinhibiting, fluids or body exudates from passing through the backsheet.In one embodiment, the size of the backsheet may be dictated by the sizeof the absorbent article and the design or configuration of theabsorbent article to be formed, for example.

The backsheet 20 may be joined with the topsheet 18. Suitable backsheetfilms include those manufactured by Tredegar Industries Inc. of TerreHaute, Ind. and sold under the trade names X15306, X10962, and X10964.Other suitable backsheet materials may include breathable materials thatpermit vapors to escape from the diaper 10 while still preventing liquidexudates from passing through the backsheet 10. Exemplary breathablematerials may include materials such as woven webs, nonwoven webs,composite materials such as film-coated nonwoven webs, and microporousfilms such as manufactured by Mitsui Toatsu Co., of Japan under thedesignation ESPOIR NO and by EXXON Chemical Co., of Bay City, Tex.,under the designation EXXAIRE. Suitable breathable composite materialscomprising polymer blends are available from Clopay Corporation,Cincinnati, Ohio under the name HYTREL blend P18-3097. Such breathablecomposite materials are described in greater detail in PCT ApplicationNo. WO 95/16746, published on Jun. 22, 1995 in the name of E. I. DuPont.Other breathable backsheets including nonwoven webs and apertured formedfilms are described in U.S. Pat. No. 5,571,096 issued to Dobrin et al.on Nov. 5, 1996.

In certain embodiments, the backsheet of the present invention may havea water vapor transmission rate (WVTR) of greater than about 2000 g/24h/m², greater than about 3000 g/24 h/m², greater than about 5000 g/24h/m², greater than about 6000 g/24 h/m², greater than about 7000 g/24h/m², greater than about 8000 g/24 h/m², greater than about 9000 g/24h/m², greater than about 10000 g/24 h/m², greater than about 11000 g/24h/m², greater than about 12000 g/24 h/m², greater than about 15000 g/24h/m², measured according to WSP 70.5 (08) at 37.8° C. and 60% RelativeHumidity.

FIG. 2 shows a cross section of FIG. 1 taken along the sectional line2-2 of FIG. 1. Starting from the wearer facing side, the diaper 10 maycomprise the topsheet 18, the components of the absorbent core 14, andthe backsheet 20. According to a certain embodiment, the diaper 10 mayalso comprise an acquisition system 50 disposed between the liquidpermeable topsheet 18 and a wearer facing side of the absorbent core 14.The acquisition system 50 may be in direct contact with the absorbentcore. The acquisition system 50 may comprise a single layer or multiplelayers, such as an upper acquisition layer 52 facing towards thewearer's skin and a lower acquisition 54 layer facing the garment of thewearer. According to a certain embodiment, the acquisition system 50 mayfunction to receive a surge of liquid, such as a gush of urine. In otherwords, the acquisition system 50 may serve as a temporary reservoir forliquid until the absorbent core 14 can absorb the liquid.

In a certain embodiment, the acquisition system 50 may comprisechemically cross-linked cellulosic fibers. Such cross-linked cellulosicfibers may have desirable absorbency properties. Exemplary chemicallycross-linked cellulosic fibers are disclosed in U.S. Pat. No. 5,137,537.According to certain embodiments, the cross-linked cellulosic fibers maybe crimped, twisted, or curled, or a combination thereof includingcrimped, twisted, and curled.

In a certain embodiment, one or both of the upper and lower acquisitionlayers 52 and 54 may comprise a non-woven, which may be hydrophilic.Further, according to a certain embodiment, one or both of the upper andlower acquisition layers 52 and 54 may comprise the chemicallycross-linked cellulosic fibers, which may or may not form part of anonwoven material. According to an exemplary embodiment, the upperacquisition layer 52 may comprise a nonwoven, without the cross-linkedcellulosic fibers, and the lower acquisition layer 54 may comprise thechemically cross-linked cellulosic fibers. Further, according to anembodiment, the lower acquisition layer 54 may comprise the chemicallycross-linked cellulosic fibers mixed with other fibers such as naturalor synthetic polymeric fibers. According to exemplary embodiments, suchother natural or synthetic polymeric fibers may include high surfacearea fibers, thermoplastic binding fibers, polyethylene fibers,polypropylene fibers, PET fibers, rayon fibers, lyocell fibers, andmixtures thereof. According to a particular embodiment, the loweracquisition layer 54 has a total dry weight, the cross-linked cellulosicfibers are present on a dry weight basis in the upper acquisition layerin an amount from about 30% to about 95% by weight of the loweracquisition layer 54, and the other natural or synthetic polymericfibers are present on a dry weight basis in the lower acquisition layer54 in an amount from about 70% to about 5% by weight of the loweracquisition layer 54.

According to a certain embodiment, the lower acquisition layer 54desirably has a high fluid uptake capability. Fluid uptake is measuredin grams of absorbed fluid per gram of absorbent material and isexpressed by the value of “maximum uptake.” A high fluid uptakecorresponds therefore to a high capacity of the material and isbeneficial, because it ensures the complete acquisition of fluids to beabsorbed by an acquisition material. According to exemplary embodiments,the lower acquisition layer 54 has a maximum uptake of about 10 g/g.

Suitable non-woven materials for the upper and lower acquisition layers52 and 54 include, but are not limited to SMS material, comprising aspunbonded, a melt-blown and a further spunbonded layer. In certainembodiments, permanently hydrophilic non-wovens, and in particular,nonwovens with durably hydrophilic coatings are desirable. Additionalsuitable embodiments may in particular be formed by a nonwoven web, suchas a carded nonwoven, a spunbond nonwoven (“S”) or a meltblown nonwoven(“M”), and laminates of any of these. For example spunmelt polypropylenenonwovens are suitable, in particular those having a laminate web SMS,or SMMS, or SSMMS, structure, and having a basis weight range of about 5gsm to 15 gsm. Suitable materials are for example disclosed in U.S. Pat.No. 7,744,576, US2011/0268932A1, US2011/0319848A1, or US2011/0250413A1.Nonwoven materials provided from synthetic fibers may be used, such aspolyethylene, polyethylene terephthalate, and in particularpolypropylene.

As polymers used for nonwoven production may be inherently hydrophobic,they may be coated with hydrophilic coatings. One way to producenonwovens with durably hydrophilic coatings, is via applying ahydrophilic monomer and a radical polymerization initiator onto thenonwoven, and conducting a polymerization activated via UV lightresulting in monomer chemically bound to the surface of the nonwoven asdescribed in co-pending U.S. Patent Publication No. 2005/0159720.Another way to produce nonwovens with durably hydrophilic coatings is tocoat the nonwoven with hydrophilic nanoparticles as described inco-pending applications U.S. Pat. No. 7,112,621 to Rohrbaugh et al. andin PCT Application Publication WO 02/064877.

Typically, nanoparticles have a largest dimension of below 750 nm.Nanoparticles with sizes ranging from 2 to 750 nm may be economicallyproduced. An advantage of nanoparticles is that many of them can beeasily dispersed in water solution to enable coating application ontothe nonwoven, they typically form transparent coatings, and the coatingsapplied from water solutions are typically sufficiently durable toexposure to water. Nanoparticles can be organic or inorganic, syntheticor natural. Inorganic nanoparticles generally exist as oxides,silicates, and/or, carbonates. Typical examples of suitablenanoparticles are layered clay minerals (e.g., LAPONITE™ from SouthernClay Products, Inc. (USA), and Boehmite alumina (e.g., Disperal P2™ fromNorth American Sasol. Inc.). According to a certain embodiment, asuitable nanoparticle coated non-woven is that disclosed in patentapplication Ser. No. 10/758,066 entitled “Disposable absorbent articlecomprising a durable hydrophilic core wrap” to Ekaterina AnatolyevnaPonomarenko and Mattias NMN Schmidt.

Further useful non-wovens are described in U.S. Pat. No. 6,645,569 toCramer et al., U.S. Pat. No. 6,863,933 to Cramer et al., U.S. Pat. No.7,112,621 to Rohrbaugh et al., and co-pending patent application Ser.No. 10/338,603 to Cramer et al. and Ser. No. 10/338,610 to Cramer et al.

In some cases, the nonwoven surface can be pre-treated with high energytreatment (corona, plasma) prior to application of nanoparticlecoatings. High energy pre-treatment typically temporarily increases thesurface energy of a low surface energy surface (such as PP) and thusenables better wetting of a nonwoven by the nanoparticle dispersion inwater.

Notably, permanently hydrophilic non-wovens are also useful in otherparts of an absorbent article. For example, topsheets and absorbent corelayers comprising permanently hydrophilic non-wovens as described abovehave been found to work well.

According to a certain embodiment, the upper acquisition layer 52 maycomprise a material that provides good recovery when external pressureis applied and removed. Further, according to a certain embodiment, theupper acquisition layer 52 may comprise a blend of different fibersselected, for example from the types of polymeric fibers describedabove. In some embodiments, at least a portion of the fibers may exhibita spiral-crimp which has a helical shape. In some embodiments, the upperacquisition layer 52 may comprise fibers having different degrees ortypes of crimping, or both. For example, one embodiment may include amixture of fibers having about 8 to about 12 crimps per inch (cpi) orabout 9 to about 10 cpi, and other fibers having about 4 to about 8 cpior about 5 to about 7 cpi. Different types of crimps include, but arenot limited to a 2D crimp or “flat crimp” and a 3D or spiral-crimp.According to a certain embodiment, the fibers may include bi-componentfibers, which are individual fibers each comprising different materials,usually a first and a second polymeric material. It is believed that theuse of side-by-side bi-component fibers is beneficial for imparting aspiral-crimp to the fibers.

The upper acquisition layer 52 may be stabilized by a latex binder, forexample a styrene-butadiene latex binder (SB latex), in a certainembodiment. Processes for obtaining such lattices are known, forexample, from EP 149 880 (Kwok) and US 2003/0105190 (Diehl et al.). Incertain embodiments, the binder may be present in the upper acquisitionlayer 52 in excess of about 12%, about 14% or about 16% by weight. Forcertain embodiments, SB latex is available under the trade name GENFLO™3160 (OMNOVA Solutions Inc.; Akron, Ohio).

Absorbent Core

The absorbent core 14 in FIGS. 1-8 generally is disposed between thetopsheet 18 and the backsheet 20 and comprises two layers, a firstabsorbent layer 60 and a second absorbent layer 62. As best shown inFIG. 3, the first absorbent layer 60 of the absorbent core 14 comprisesa substrate 64, an absorbent particulate polymer material (such as asuperabsorbent polymer material) 66 on the substrate 64, and athermoplastic composition (such as a fiberized net structure) 68 on theabsorbent particulate polymer material 66 and at least portions of thefirst substrate 64 as a means for covering and immobilizing theabsorbent particulate polymer material 66 on the first substrate 64.According to another embodiment illustrated in FIG. 4, the firstabsorbent layer 60 of the absorbent core 14 may also include a coverlayer 70 on the thermoplastic composition 68.

Likewise, as best illustrated in FIG. 2, the second absorbent layer 62of the absorbent core 14 may also include a substrate 72, an absorbentparticulate polymer material (such as a superabsorbent polymer material)74 on the second substrate 72, and a thermoplastic composition (such asa fiberized net structure) 76 on the absorbent particulate polymermaterial 74 and at least a portion of the second substrate 72 forimmobilizing the absorbent particulate polymer material 74 on the secondsubstrate 72. Although not illustrated, the second absorbent layer 62may also include a cover layer such as the cover layer 70 illustrated inFIG. 4. The first and second absorbent layers may be combined togethersuch that at least a portion of the fiberized net structure of the firstabsorbent layer contacts at least a portion of the fiberized netstructure of the second absorbent layer.

The substrate 64 of the first absorbent layer 60 may be referred to as adusting layer, in other embodiments a core cover, and has a firstsurface or outer surface 78 which faces the backsheet 20 of the diaper10 and a second surface or inner surface 80 which faces the absorbentparticulate polymer material 66. Likewise, the substrate 72 of thesecond absorbent layer 62 may be referred to as a core cover and has afirst surface or outer surface 82 facing the topsheet 18 of the diaper10 and a second surface or inner surface 84 facing the absorbentparticulate polymer material 74. In some embodiments, the firstsubstrate 64 and the second substrate 72 may both be core covers or corewrap material. The first and second substrates 64 and 72 may be adheredto one another with adhesive about the periphery to form an envelopeabout the absorbent particulate polymer materials 66 and 74 to hold theabsorbent particulate polymer material 66 and 74 within the absorbentcore 14. The absorbent core may then have a front edge 35, a back edge37, and two side edges 39. The bonded periphery at the front edge 35 mayform a front end seal and the bonded periphery at the back edge 37 mayform a back end seal. The thermoplastic composition 68, 76 may in someembodiments be an adhesive material. Any suitable adhesive can be usedfor this, for example so-called hotmelt adhesives.

According to a certain embodiment, the substrates 64 and 72 of the firstand second absorbent layers 60 and 62 may be a nonwoven material, suchas those nonwoven materials described above. In certain embodiments, thenonwovens are porous and in one embodiment has a pore size of about 32microns.

The thermoplastic composition 68 and 76 may serve to cover and at leastpartially immobilize the absorbent particulate polymer material 66 and74. In one embodiment of the present invention, the thermoplasticcomposition 68 and 76 can be disposed essentially uniformly within theabsorbent particulate polymer material 66 and 74, between the particlesof the superabsorbent material. However, in a certain embodiment, thethermoplastic composition 68 and 76 may be provided as a fibrous netstructure which is at least partially in contact with the absorbentparticulate polymer material 66 and 74 and partially in contact with thesubstrate layers 64 and 72 of the first and second absorbent layers 60and 62. FIGS. 3, 4, and 7 show such a structure, and in that structure,the absorbent particulate polymer material 66 and 74 is provided as adiscontinuous layer, and a layer of fibrous thermoplastic composition 68and 76 is laid down onto the layer of absorbent particulate polymermaterial 66 and 74, such that the thermoplastic composition 68 and 76 isin direct contact with the absorbent particulate polymer material 66 and74, but also in direct contact with the second surfaces 80 and 84 of thesubstrates 64 and 72, where the substrates are not covered by theabsorbent particulate polymer material 66 and 74. The fiberized netstructures of each substrate, 68 and 76, may essentially be onefiberized net structure, each contacting the other. This imparts anessentially three-dimensional structure to the fibrous net structures 68and 76, which in itself is essentially a two-dimensional structure ofrelatively small thickness, as compared to the dimension in length andwidth directions. In other words, the thermoplastic composition 68 and76 undulates between the absorbent particulate polymer material 66 and74 and the second surfaces of the substrates 64 and 72, forming afiberized net structure 68 and 76.

The thermoplastic composition 68 and 76 may provide cavities to coverthe absorbent particulate polymer material 66 and 74, and therebyimmobilize the material. In a further aspect, the thermoplasticcomposition 68 and 76 may bond to the substrates 64 and 72 and thusaffix the absorbent particulate polymer material 66 and 74 to thesubstrates 64 and 72. Thus, in accordance with certain embodiments, thethermoplastic composition 68 and 76 immobilizes the absorbentparticulate polymer material 66 and 74 when wet, such that the absorbentcore 14 achieves an absorbent particulate polymer material loss of nomore than about 70%, 60%, 50%, 40%, 30%, 20%, 10% according to the WetImmobilization Test described herein. Some thermoplastic compositionswill also penetrate into both the absorbent particulate polymer material66 and 74 and the substrates 64 and 72, thus providing for furtherimmobilization and affixation. Of course, while the thermoplasticcompositions disclosed herein provide a much improved wet immobilization(i.e., immobilization of absorbent material when the article is wet orat least partially loaded), these thermoplastic compositions may alsoprovide a very good immobilization of absorbent material when theabsorbent core 14 is dry. The thermoplastic adhesive material 68 and 76may also be referred to as a hot melt adhesive. As noted above, in someembodiments, the thermoplastic composition is an adhesive, and in otherembodiments, it may be a fiberized net structure, a film, nanofibers,and/or other forms.

The thermoplastic composition may function as a fibrous structure thatentraps the absorbent particulate polymer 66 and prevents substantialmovement. Thermoplastic compositions most useful for immobilizing theabsorbent particulate polymer material 66 and 74 combine good cohesionand good flexibility to reduce the likelihood that the thermoplasticcomposition breaks in response to strain. Good adhesion ability maypromote good contact between the thermoplastic composition 68 and 76 andthe absorbent particulate polymer material 66 and 74 and the substrates64 and 72. When the absorbent core 14 absorbs liquid, the absorbentparticulate polymer material 66 and 74 swells and subjects thethermoplastic composition 68 and 76 to external forces. In certainembodiments, the thermoplastic composition 68 and 76 may allow for suchswelling, without imparting too many compressive forces, which wouldrestrain the absorbent particulate polymer material 66 and 74 fromswelling. Elasticity and flexibility in the thermoplastic compositionalso promotes overall article flexibility and its preferred ability toconform to the wearer. The thermoplastic composition may have high G′values, but may still be not too stiff to work as a fiberized structurein absorbent articles. A composition with a relatively high G′, such asgreater than 1.2×10⁶ Pa, means a stiffer composition. The thermoplasticcompositions in the present invention may be less dense, thus providingmore volume at the same basis weight. This is particularly true forcompositions comprising polyolefins.

The absorbent core 14 may also comprise an auxiliary adhesive which isnot illustrated in the figures. The auxiliary adhesive may be depositedon the first and second substrates 64 and 72 of the respective first andsecond absorbent layers 60 and 62 before application of the absorbentparticulate polymer material 66 and 74 for enhancing adhesion of theabsorbent particulate polymer materials 66 and 74 and the thermoplasticcomposition 68 and 76 to the respective substrates 64 and 72. It may bepreferable to deposit the auxiliary adhesive on a nonwoven that is themost hydrophilic for improved bonding. The auxiliary glue may also aidin immobilizing the absorbent particulate polymer material 66 and 74 andmay comprise the same thermoplastic composition as described hereinaboveor may also comprise other or additional adhesives including but notlimited to sprayable hot melt adhesives. The auxiliary glue may beapplied to the substrates 64 and 72 by any suitable means, but accordingto certain embodiments, may be applied in about 0.5 to about 1 mm wideslots spaced about 0.5 to about 2 mm apart.

In some embodiments, the absorbent core may comprise a singlethermoplastic composition that acts in some places as a fiberized netstructure and in other places as a more traditional hot melt adhesive.For example, such a thermoplastic composition may provide theimmobilization of the absorbent particulate polymer material 66 asdiscussed above, while also providing adhesive strength for the frontend seal and back end seal, for the side edges of the core, and/or forthe substrates 64 and 72 in general, such as discussed for the auxiliaryadhesive. In some situations, no auxiliary adhesive would be necessary.In other embodiments, one thermoplastic composition may be used toprovide a fiberized net structure to immobilize the absorbentparticulate polymer, while an auxiliary adhesive is used in conjunctionwith the thermoplastic composition to adhere materials in other areas inthe core.

The fiberized net structure composition and/or any hot melt adhesive maybe applied in the absorbent particulate polymer material area at a basisweight of from about 2 grams/meter² to about 7 grams/meter² (gsm), insome embodiments from about 2 gsm to about 9 gsm, or from about 4 gsm toabout 9 gsm. This may be a combined basis weight from application on afirst and a second substrate, for example, 4 and 3 gsm, respectively, or5 and 4 gsm, respectively. The auxiliary adhesive may be applied in theabsorbent particulate polymer material area in any amount from 0 toabout 8 gsm, in some embodiments, about 5 gsm, in other embodimentsabout 8 gsm. The total amount of adhesive and fiberized net structurematerial may be from about 2 gsm to about 15 gsm in the absorbentparticulate polymer material area. The front end seal may have fromabout 10 gsm to about 35 gsm of adhesive. Similarly, the back end sealmay have from about 10 gsm to about 35 gsm of adhesive. In someembodiments, either or both of the front and back end seals may havefrom about 5 gsm to 15 gsm of adhesive. In some embodiments, the amountof adhesive in an end seal may be a combination of the fiberized netstructure composition, the auxiliary adhesive, and the end sealadhesive.

In certain embodiments, the thermoplastic composition 68 and 76 maycomprise, in its entirety, a single thermoplastic polymer or a blend ofthermoplastic polymers, having a softening point, as determined by theASTM Method D-28-99 “Ring and Ball Softening Point”, in the rangebetween 50° C. and 300° C., in some embodiments in the range between 75and 150° C., or alternatively the thermoplastic composition may be a hotmelt adhesive comprising at least one thermoplastic polymer incombination with other thermoplastic diluents such as tackifying resins,plasticizers and additives such as antioxidants. In certain embodiments,the thermoplastic polymer composition has typically a molecular weight(Mw) of more than 10,000 and a glass transition temperature (Tg) usuallybelow room temperature or −20° C.>Tg<18° C. In certain embodiments,typical concentrations of the polymer in a hot melt are in the range ofabout 10 to about 60% by weight. In certain embodiments, thermoplasticpolymers may be water insensitive.

Suitable thermoplastic polymers that may be employed are metallocenepolyolefins, such as ethylene polymers prepared using single-site ormetallocene catalysts. Therein, at least one comonomer can bepolymerized with ethylene to make a copolymer, terpolymer or higherorder polymer. Also applicable are amorphous polyolefins or amorphouspolyalphaolefins (APAO) which are homopolymers, copolymers orterpolymers of C2 to C8 alpha olefins. Also suitable thermoplasticpolymers may include styrenic block copolymers, such as SIS, SEBS, andSBS, combinations of styrenic block copolymers, and combinations ofstyrenic block copolymers and polyolefins.

Also suitable, for example, is NW1414 available from H.B. FullerCompany. Also appropriate are propylene-based polymers. Thethermoplastic polymers, thermoplastic composition, and/or any auxiliaryadhesive may be exemplified by the materials described in U.S.2014/0358100. The material may include two different propylene-basedpolymers. The propylene-based polymers may be propylene homopolymers, orone or more of the two different propylene-based polymers may becopolymers with one or more other monomers (e.g., ethylene, butene,pentene, octene, etc.). The propylene-based polymers may be basedentirely on olefins, i.e., do not contain any functional groups. Thepropylene-based polymers may comprise greater than about 75% by weightpropylene or even greater than about 80% by weight propylene. Thepropylene-based polymers may have a polydispersity (Mw/Mn) of less thanabout 5, less than about 3, or even about 2. Propylene-based polymersmay have a density of no greater than about 0.89, or no greater thanabout 0.88. The thermoplastic composition and/or adhesives may comprisea first propylene-based polymer that has a Mw (molecular weight) of atmost about 75,000, at most about 60,000, at most about 50,000, orbetween about 30,000 and about 70,000, wherein the first propylene-basedpolymer may be present in the overall composition in an amount of atleast about 20%, 25%, or 30% by weight, or from about 15% to about 50%by weight, or from about 25% to about 45% by weight. Exemplary firstpolymers may include LICOCENE PP1602 and LICOCENE PP2602 both availablefrom Clariant International Ltd. (Muttenz, Switzerland) and L-MODU X400Sand L-MODU X600S available from Idemitsu Kosan Co., Ltd. (Japan). Thecomposition may also comprise a second propylene-based polymer that hasa Mw of at least about 100,000, at least about 125,000, at least about150,000, or between about 125,000 and about 400,000, or between about150,000 and about 250,000. The second propylene-based polymer may bepresent in the composition in an amount of at most about 20% by weight,at most about 15%, by weight, at most about 8% by weight, or from about2% by weight to about 15% by weight, or from about 3% by weight to about10% by weight. Exemplary second polymers may include VISTAMAXX 6202 andVISTAMAXX 6102 available from ExxonMobil Chemical (Houston, Tex.) andVERSIFY 3300 available from Dow Chemical Company (Houston, Tex.). Thetotal propylene-based polymer content of a composition may be at leastabout 20% by weight, at least about 25% by weight, at least about 30% byweight, at least about 35% by weight, or from about 35% by weight toabout 50% by weight. The composition may include a third polymer, suchas a styrenic block copolymer, which may be hydrogenated. Usefulhydrogenated styrene block copolymers include, e.g.,styrene-ethylene/butadiene-styrene block copolymer,styrene-ethylene/propylene-styrene block copolymer,styrene-ethylene/ethylene-propylene-styrene block copolymer, andcombinations thereof. The styrenic block copolymer may have a styrenecontent of less than about 20% by weight, less than about 18% by weight,or even less than about 15% by weight. The styrene block copolymer mayalso have a Melt Flow when tested according to ASTM 1238 (230° C., 5 kg)of less than about 25 g/10 min, less than about 20 g/10 min, less thanabout 10 g/10 min, or even less than about 5 g/10 min. Exemplaryhydrogenated styrene block copolymers are commercially available under avariety of trade designations including, e.g., the SEPTON series oftrade designations from Kuraray Co., Ltd (Houston, Tex.) including,e.g., SEPTON S2063 and S2007 hydrogenated styrene-isoprene-styrene blockcopolymers, the KRATON G series of trade designations from KratonPerformance Polymers Inc. (Houston, Tex.) including, e.g., KRATON G1645M, KRATON G 1657 styrene-ethylene/butadiene-styrene blockcopolymers. The materials may include no greater than about 20% byweight, no greater than about 15% by weight, from about 2% to 20% byweight, or even from about 5% to 15% by weight of the third polymer.Also, the composition may include and crystalline polyethylene oxide. Insome embodiments, the tackifying resin has a Mw below 5,000 and a Tgabove room temperature, with concentrations of the resin in a hot meltare in the range of about 30 to about 60%. Suitable classes oftackifying resins include, for example, aromatic, aliphatic andcycloaliphatic hydrocarbon resins, mixed aromatic and aliphatic modifiedhydrocarbon resins, aromatic modified aliphatic hydrocarbon resins, andhydrogenated versions thereof terpenes, modified terpenes andhydrogenated versions thereof natural rosins, modified rosins, rosinesters, and hydrogenated versions thereof, and combinations thereof.Suitable tackifying agents include, for example, the ESCOREZ series oftrade designations from Exxon Mobil Chemical Company (Houston, Tex.)including ESCOREZ 5400 and ESCOREZ 5600, the EASTOTAC series of tradedesignations from Eastman Chemical (Kingsport, Tenn.) including EASTOTACH-100R and EASTOTAC H-100L, and the WINGTACK series of tradedesignations from Cray Valley HSC (Exton, Pa.) including WINGTACK 86,WINGTACK EXTRA, and WINTACK 95 and the PICCOTAC and KRISTALEX series oftrade designations from Eastman Chemical Company (Kingsport, Tenn.)including, e.g., PICCOTAC 8095 and KRISTALEX 3100. In some embodiments,the composition may comprise from at least about 10% by weight, at leastabout 20% by weight, or from about 5% by weight to about 60% by weight,or from about 10% by weight to about 40% by weight tackifying agent. Insome embodiments, the thermoplastic composition, either in an adhesiveform or as a fiberized net structure, may be free of any tackifyingagent, or may be substantially tackifier-free.

In some embodiments, the plasticizer has a low Mw of typically less than1,000 and a Tg below room temperature, with a typical concentration ofabout 0 to about 20%, in some embodiments, about 10 to about 20%.Suitable plasticizers include, for example, naphthenic oils, paraffinicoils (e.g., cycloparaffin oils), mineral oils, paraffinic adipateesters, olefin oligomers (e.g., oligomers of polypropylene, polybutene,and hydrogenated polyisoprene), polybutenes, polyisoprene, hydrogenatedpolyisoprene, polybutadiene, benzoate esters, animal oil, plant oils(e.g. castor oil, soybean oil), derivatives of oils, glycerol esters offatty acids, polyesters, polyethers, lactic acid derivatives andcombinations thereof. Exemplary commercially available plasticizersinclude CALSOL 550 oil from Calumet Specialty Products Partners, LP(Indianapolis, Ind.), KAYDOL OIL from Sonneborn (Tarrytown N.Y.) PARAPOLpolybutene from Exxon Mobil Chemical Company (Houston, Tex.), OPPANOLpolyisobutylene from BASF (Ludwigsjhafen, Germany), KRYSTOL 550 mineraloil from Petrochem Carless Limited (Surrey, England) and PURETOL 15mineral oil from Petro Canada Lubricants Inc. (Mississauga, Ontario).The plasticizer may be present in an amount at most about 25% by weight,20% by weight, 18% by weight, or from about 5% to about 30% by weight,or from about 10% to about 20% by weight. The adhesive/fiberized netstructure composition may include a wax. Useful classes of wax mayinclude, e.g., paraffin waxes, microcrystalline waxes, high density lowmolecular weight polyethylene waxes, by-product polyethylene waxes,polypropylene waxes, Fischer-Tropsch waxes, oxidized Fischer-Tropschwaxes, functionalized waxes such as acid, anhydride, and hydroxylmodified waxes, animal waxes, vegetable waxes (e.g., soy wax) andcombinations thereof. Useful waxes are commercially available from avariety of suppliers including EPOLENE N and C series of tradedesignations from Westlake Chemical Corporation (Houston, Tex.)including e.g., EPOLENE N-21 and the LICOCENE series of tradedesignations from Clariant International Ltd. (Muttenz, Switzerland)including e.g. TP LICOCENE PP 6102. The composition may include nogreater than about 10% by weight, no greater than about 5% by weight,from about 1% by weight to about 10% by weight, or even from about 1% toabout 5% by weight wax. The adhesive/fiberized net structure compositionmay also include additional components including, e.g., stabilizers,antioxidants, additional polymers (e.g., styrenic block copolymers,amorphous poly-alpha olefins, polyethylene copolymers), adhesionpromoters, ultraviolet light stabilizers, corrosion inhibitors,colorants (e.g., pigments and dyes), fillers, surfactants, wetnessindicators, superabsorbents and combinations thereof. Usefulantioxidants include, e.g., pentaerythritoltetrakis[3,(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],2,2′-methylene bis(4-methyl-6-tert-butylphenol), phosphites including,e.g., tris-(p-nonylphenyl)-phosphite (TNPP) andbis(2,4-di-tert-butylphenyl)4,4′-diphenylene-diphosphonite,di-stearyl-3,3′-thiodipropionate (DSTDP), and combinations thereof.Useful antioxidants are commercially available under a variety of tradedesignations including, e.g., the IRGANOX series of trade designationsincluding, e.g., IRGANOX 1010, IRGANOX 565, and IRGANOX 1076 hinderedphenolic antioxidants and IRGAFOS 168 phosphite antioxidant, all ofwhich are available from BASF Corporation (Florham Park, N.J.), andETHYL 702 4,4′-methylene bis(2,6-di-tert-butylphenol). When present, thecomposition preferably includes from about 0.1% by weight to about 2% byweight antioxidant.

The thermoplastic composition 68, 76 may in some embodiments be anadhesive material. Any suitable adhesive can be used for this, forexample so-called hotmelt adhesive. For example, Henkel DM3800, can beused. In certain embodiments, the thermoplastic composition 68 and 76 ispresent in the form of fibers. In some embodiments, the fiberized netstructure will have a range of thickness from about 1 to about 90micrometers, in some embodiments, from about 1 to about 75 micrometers,in some embodiments from about 1 to about 50 micrometers, and in stillother embodiments from about 1 to about 35 micrometers, and an averagemaximum fiber-to-fiber distance of about 0.1 mm to about 5 mm or about0.3 mm to about 6 mm. The average fiber thickness may be about 30micrometers, or may be from about 15 to about 45 micrometers. To improvethe adhesion of the thermoplastic composition as an adhesive material tothe substrates 64 and 72 or to any other layer, in particular any othernon-woven layer, such layers may be pre-treated with an auxiliaryadhesive.

The fiberized net structure may consist of continuous extrudedpolymer/adhesive strands, which create a net structure with irregularstrand or filament thickness or with irregular open areas (pores ormaximum strand to strand distance). Continuous polymer/adhesive strandsmay overlap and form strand crossings or overlaps with differentdiameters. The applied fiberized net structure may build athree-dimensional net in the absorbent core as described herein. Atequivalent basis weights, a fiberized net structure with thicker fibersmay be more open and irregular than a fiberized net structure withthinner fibers. It is believed that the thicker fibers can maintain heatin the fiber longer, which can allow the fiberized net structure to wetand penetrate a nonwoven better, allowing for better bond strength.

If, for example, the core has channels (as discussed below) and thechannels are then more secure, that is, are permanent channels, the moreopen structure of the fiberized net structure allows the AGM orsuperabsorbent polymer material to adjust or move within its confinedarea.

In certain embodiments, the thermoplastic composition 68 and 76, and/orany auxiliary adhesive, will meet at least one, or several, or all ofthe following parameters:

An exemplary thermoplastic composition 68 and 76 may have a storagemodulus G′ measured at 21° C. of at least about 1.2×10⁶ Pa as measuredby the test method detailed below. It is unexpected that thethermoplastic compositions of the present invention have high G′ valuesbut are not too stiff to work as a fiberized net structure or a hot meltadhesive in absorbent articles. An adhesive with a relatively high G′,such as greater than 1.2×10⁶ Pa, means a stiffer adhesive.

When the absorbent article contains channels, the thermoplasticcomposition and/or adhesive material(s) may not only help inimmobilizing the absorbent material on the supporting sheet orsubstrate, but it may also help in maintaining the integrity of thechannels in the absorbent structure absorbent core during storage and/orduring use of the disposable article. The thermoplastic and/or adhesivematerials may help to avoid that a significant amount of absorbentmaterial migrates into the channels. Furthermore, when the materials areapplied in the channels or on the supporting sheet portions coincidingwith the channels it may thereby help to adhere the substrate of theabsorbent structure to said walls, and/or to a further material, as willbe described in further details below. In some embodiments, an adhesivemay be a thermoplastic adhesive material. That is, in some embodiments,a thermoplastic composition may be applied as fibers, forming a fibrousnetwork that immobilizes the absorbent material on the substrates, orsupporting sheet as discussed below. The thermoplastic fibers may bepartially in contact with the substrate of the absorbent structure; ifapplied also in the channels, it (further) anchors the absorbent layerto the substrate.

The thermoplastic composition material may for example allow for suchswelling, without breaking and without imparting too many compressiveforces, which would restrain the absorbent polymer particles fromswelling.

A typical parameter for a thermoplastic composition suitable for use inthe present disclosure can be a loss Factor tan δ at 60° C. (6.28mrad/s) of below the value of 1, or below the value of 0.5. The lossFactor tan δ at 60° C. is correlated with the cohesive character of anadhesive at elevated ambient temperatures. The lower tan δ, the more anadhesive behaves like a solid rather than a liquid, i.e. the lower itstendency to flow or to migrate and the lower the tendency of an adhesivesuperstructure as described herein to deteriorate or even to collapseover time. This value is hence particularly important if the absorbentarticle is used in a hot climate.

It may be beneficial, e.g. for process reasons and/or performancereasons, that the thermoplastic adhesive material has a viscosity ofbetween 800 and 8000 mPa·s, or from 1000 mPa·s to 6000 mPa·s or from1500 mPa·s to 7000 mPa·s or to 5000 mPa·s or to 3000 mPa·s or to 2500mPa·s, at 163° C., as measurable by ASTM D3236-88, using spindle 27, 20pmp, 20 minutes preheating at the temperature, and stirring for 10 min.

The thermoplastic composition may have a softening point of between 60°C. and 150° C., or between 75° C. and 135° C., or between 90° C. and130° C., or between 100° C. and 115° C., as can be determined with ASTME28-99 (Herzog method; using glycerine).

In one embodiment herein, the thermoplastic component may behydrophilic, having a contact angle of less than 90°, or less than 80°or less than 75° or less than 70°, as measurable with ASTM D 5725-99.

The cover layer 70 shown in FIG. 4 may comprise the same material as thesubstrates 64 and 72, or may comprise a different material. In certainembodiments, suitable materials for the cover layer 70 are the non-wovenmaterials, typically the materials described above as useful for thesubstrates 64 and 72. The nonwovens may be hydrophilic and/orhydrophobic.

A printing system 130 for making an absorbent core 14 in accordance withan embodiment of this invention is illustrated in FIG. 11 and maygenerally comprise a first printing unit 132 for forming the firstabsorbent layer 60 of the absorbent core 14 and a second printing unit134 for forming the second absorbent layer 62 of the absorbent core 14.

The first printing unit 132 may comprise a first auxiliary adhesiveapplicator 136 for applying an auxiliary adhesive to the substrate 64,which may be a nonwoven web, a first rotatable support roll 140 forreceiving the substrate 64, a hopper 142 for holding absorbentparticulate polymer material 66, a printing roll 144 for transferringthe absorbent particulate polymer material 66 to the substrate 64, and athermoplastic composition material applicator 146 for applying thethermoplastic composition material 68 to the substrate 64 and theabsorbent particulate polymer 66 material thereon.

The second printing unit 134 may comprise a second auxiliary adhesiveapplicator 148 for applying an auxiliary adhesive to the secondsubstrate 72, a second rotatable support roll 152 for receiving thesecond substrate 72, a second hopper 154 for holding the absorbentparticulate polymer material 74, a second printing roll 156 fortransferring the absorbent particulate polymer material 74 from thehopper 154 to the second substrate 72, and a second thermoplasticcomposition material applicator 158 for applying the thermoplasticcomposition material 76 to the second substrate 72 and the absorbentparticulate polymer material 74 thereon.

The printing system 130 also includes a guide roller 160 for guiding theformed absorbent core from a nip 162 between the first and secondrotatable support rolls 140 and 152.

The first and second auxiliary applicators 136 and 148 and the first andsecond thermoplastic composition material applicators 146 and 158 may bea nozzle system which can provide a relatively thin but wide curtain ofthermoplastic composition material. In some embodiments, a contactapplication such as a slot gun may be used, while other embodiments maybe contactless (spray glue) applications. In some cases, only one of theauxiliary applicators 136 and 148 may be switched on, while in othercases both may be on at the same time, depending on the adhesive design.

As illustrated in FIGS. 1-8, the absorbent particulate polymer material66 and 74 is deposited on the respective substrates 64 and 72 of thefirst and second absorbent layers 60 and 62 in clusters 90 of particlesto form a grid pattern 92 comprising land areas 94 and junction areas 96between the land areas 94. As defined herein, land areas 94 are areaswhere the fiberized net structure does not contact the nonwovensubstrate or the auxiliary adhesive directly; junction areas 96 areareas where the thermoplastic adhesive material does contact thenonwoven substrate or the auxiliary adhesive (discussed below) directly;junction areas 96 are areas where the fiberized net structure doescontact the nonwoven substrate or the auxiliary adhesive directly. Thejunction areas 96 in the grid pattern 92 contain little or no absorbentparticulate polymer material 66 and 74. The land areas 94 and junctionareas 96 can have a variety of shapes including, but not limited to,circular, oval, square, rectangular, triangular, and the like.

The grid pattern shown in FIG. 8 is a square grid with regular spacingand size of the land areas. Other grid patterns including hexagonal,rhombic, orthorhombic, parallelogram, triangular, rectangular, andcombinations thereof may also be used. The spacing between the gridlines may be regular or irregular.

The size of the land areas 94 in the grid patterns 92 may vary.According to certain embodiments, the width 119 of the land areas 94 inthe grid patterns 92 ranges from about 8 mm to about 12 mm. In a certainembodiment, the width of the land areas 94 is about 10 mm. The junctionareas 96, on the other hand, in certain embodiments, have a width orlarger span of less than about 5 mm, less than about 3 mm, less thanabout 2 mm, less than about 1.5 mm, less than about 1 mm, or less thanabout 0.5 mm.

As shown in FIG. 8, the absorbent core 14 has a longitudinal axis 100extending from a rear end 102 to a front end 104 and a transverse axis106 perpendicular to the longitudinal axis 100 extending from a firstedge 108 to a second edge 110. The grid pattern 92 of absorbentparticulate polymer material clusters 90 is arranged on the substrates64 and 72 of the respective absorbent layers 60 and 62 such that thegrid pattern 92 formed by the arrangement of land areas 94 and junctionareas 96 forms a pattern angle 112. The pattern angle 112 may be 0,greater than 0, or 15 to 30 degrees, or from about 5 to about 85degrees, or from about 10 to about 60 degrees, or from about 15 to about30 degrees.

As best seen in FIGS. 7a, 7b , and 8, the first and second layers 60 and62 may be combined to form the absorbent core 14. The absorbent core 14has an absorbent particulate polymer material area 114 bounded by apattern length 116 and a pattern width 118. The extent and shape of theabsorbent particulate polymer material area 114 may vary depending onthe desired application of the absorbent core 14 and the particularabsorbent article in which it may be incorporated. In a certainembodiment, however, the absorbent particulate polymer material area 114extends substantially entirely across the absorbent core 14, such as isillustrated in FIG. 8.

The first and second absorbent layers 60 and 62 may be combined togetherto form the absorbent core 14 such that the grid patterns 92 of therespective first and second absorbent layers 62 and 64 are offset fromone another along the length and/or width of the absorbent core 14. Therespective grid patterns 92 may be offset such that the absorbentparticulate polymer material 66 and 74 is substantially continuouslydistributed across the absorbent particulate polymer area 114. In acertain embodiment, absorbent particulate polymer material 66 and 74 issubstantially continuously distributed across the absorbent particulatepolymer material area 114 despite the individual grid patterns 92comprising absorbent particulate polymer material 66 and 74discontinuously distributed across the first and second substrates 64and 72 in clusters 90. In a certain embodiment, the grid patterns may beoffset such that the land areas 94 of the first absorbent layer 60 facethe junction areas 96 of the second absorbent layer 62 and the landareas of the second absorbent layer 62 face the junction areas 96 of thefirst absorbent layer 60. When the land areas 94 and junction areas 96are appropriately sized and arranged, the resulting combination ofabsorbent particulate polymer material 66 and 74 is a substantiallycontinuous layer of absorbent particular polymer material across theabsorbent particulate polymer material area 114 of the absorbent core 14(i.e. first and second substrates 64 and 72 do not form a plurality ofpockets, each containing a cluster 90 of absorbent particulate polymermaterial 66 therebetween). In a certain embodiment, respective gridpatterns 92 of the first and second absorbent layer 60 and 62 may besubstantially the same.

In a certain embodiment as illustrated in FIG. 8, the amount ofabsorbent particulate polymer material 66 and 74 may vary along thelength 116 of the grid pattern 92. In a certain embodiment, the gridpattern may be divided into absorbent zones 120, 122, 124, and 126, inwhich the amount of absorbent particulate polymer material 66 and 74varies from zone to zone. As used herein, “absorbent zone” refers to aregion of the absorbent particulate polymer material area havingboundaries that are perpendicular to the longitudinal axis shown in FIG.8. The amount of absorbent particulate polymer material 66 and 74 may,in a certain embodiment, gradually transition from one of the pluralityof absorbent zones 120, 122, 124, and 126 to another. This gradualtransition in amount of absorbent particulate polymer material 66 and 74may reduce the possibility of cracks forming in the absorbent core 14.

The amount of absorbent particulate polymer material 66 and 74 presentin the absorbent core 14 may vary, but in certain embodiments, ispresent in the absorbent core in an amount greater than about 80% byweight of the absorbent core, or greater than about 85% by weight of theabsorbent core, or greater than about 90% by weight of the absorbentcore, or greater than about 95% by weight of the core. In a particularembodiment, the absorbent core 14 consists essentially of the first andsecond substrates 64 and 72, the absorbent particulate polymer material66 and 74, and the thermoplastic composition 68 and 76. In anembodiment, the absorbent core 14 may be substantially cellulose free.

According to certain embodiments, the weight of absorbent particulatepolymer material 66 and 74 in at least one freely selected first squaremeasuring 1 cm×1 cm may be at least about 10%, or 20%, or 30%, 40% or50% higher than the weight of absorbent particulate polymer material 66and 74 in at least one freely selected second square measuring 1 cm×1cm. In a certain embodiment, the first and the second square arecentered about the longitudinal axis.

The absorbent particulate polymer material area, according to anexemplary embodiment, may have a relatively narrow width in the crotcharea of the absorbent article for increased wearing comfort. Hence, theabsorbent particulate polymer material area, according to an embodiment,may have a width as measured along a transverse line which is positionedat equal distance to the front edge and the rear edge of the absorbentarticle, which is less than about 100 mm, 90 mm, 80 mm, 70 mm, 60 mm oreven less than about 50 mm.

It has been found that, for most absorbent articles such as diapers, theliquid discharge occurs predominately in the front half of the diaper.The front half of the absorbent core 14 should therefore comprise mostof the absorbent capacity of the core. Thus, according to certainembodiments, the front half of said absorbent core 14 may comprise morethan about 60% of the superabsorbent material, or more than about 65%,70%, 75%, 80%, 85%, or 90% of the superabsorbent material.

The absorbent core of the invention may comprise a core wrap enclosingthe absorbent material. In some embodiments, the core wrap may be boththe first and second substrates. The core wrap may be formed by twosubstrates, typically nonwoven material which may be at least partiallysealed along the sides of the absorbent core. The first nonwoven maysubstantially form the top side of the core wrap and the second nonwovensubstantially the bottom side of the core wrap. The core wrap may be atleast partially sealed along its front side, back side and/or twolongitudinal sides to improve the containment of the absorbent materialduring use. A C-wrap seal may be for example provided on thelongitudinal sides of the core if improved containment is desired.Exemplary C-wrap description may be found in U.S. application Ser. No.14/560,211. Typical core wraps comprise two substrates which areattached to one another, but the core wrap may also be made of a singlesubstrate folded around the absorbent material, or may comprises severalsubstrates. When two substrates are used, these may be typicallyattached to another along at least part of the periphery of theabsorbent core to form a seal. Typically neither first nor secondsubstrates need to be shaped, so that they can be rectangularly cut forease of production but other shapes are not excluded.

The substrates are advantageously attached to another to form a sealalong all the edges of the core. Typical seals are the so-called C-wrapand sandwich wrap. In a C-wrap, one of the substrate, e.g. the firstsubstrate, has flaps extending over the opposed edges of the core whichare then folded over the other substrate. These flaps are bonded to theexternal surface of the other substrate, typically by adhesive. This socalled C-wrap construction can provide benefits such as improvedresistance to bursting in a wet loaded state compared to a sandwichseal.

The front side and back side of the core wrap may then also be sealedfor example by adhering the first substrate and second substrate toanother to provide complete enclosing of the absorbent material acrossthe whole of the periphery of the core. For the front side and back sideof the core, the first and second substrate may extend and be joinedtogether in a substantially planar direction, forming a so-calledsandwich construction. In the so-called sandwich seal construction, thefirst and second substrates both have material extension outwardly ofthe absorbent material deposition area which are then sealed flat alongthe whole or parts of the periphery of the core typically by gluingand/or heat/pressure bonding.

The terms “seal” and “enclosing” are to be understood in a broad sense.The seal does not need to be continuous along the whole periphery of thecore wrap but may be discontinuous along part or the whole of it, suchas formed by a series of seal points spaced on a line. Typically a sealmay be formed by gluing and/or thermal bonding. The core wrap may alsobe formed by a single substrate which may enclose the absorbent materialas in a parcel wrap and be for example sealed along the front side andback side of the core and one longitudinally extending seal.

The core wrap may be formed by any materials suitable for enclosing theabsorbent material. Typical substrate materials used in the productionof conventional cores may be used, in particular nonwovens but alsopaper, tissues, films, wovens, or laminate of any of these. The corewrap may in particular be formed by a nonwoven web, such as a cardednonwoven, a spunbond nonwoven (“S”) or a meltblown nonwoven (“M”), andlaminates of any of these. For example spunmelt polypropylene nonwovensare suitable, in particular those having a laminate web SMS, or SMMS, orSSMMS, structure, and having a basis weight range of about 5 gsm to 15gsm. Suitable materials are for example disclosed in U.S. Pat. No.7,744,576, US2011/0268932A1, US2011/0319848A1, or US2011/0250413A1.Nonwoven materials provided from synthetic fibers may be used, such aspolyethylene, Polyethylene terephthalate, and in particularpolypropylene.

In certain embodiments, the absorbent core 14 may further comprise anyabsorbent material that is generally compressible, conformable,non-irritating to the wearer's skin, and capable of absorbing andretaining liquids such as urine and other certain body exudates. In suchembodiments, the absorbent core 14 may comprise a wide variety ofliquid-absorbent materials commonly used in disposable diapers and otherabsorbent articles such as comminuted wood pulp, which is generallyreferred to as airfelt, creped cellulose wadding, melt blown polymers,including co-form, chemically stiffened, modified or cross-linkedcellulosic fibers, tissue, including tissue wraps and tissue laminates,absorbent foams, absorbent sponges, or any other known absorbentmaterial or combinations of materials. The absorbent core 14 may furthercomprise minor amounts (typically less than about 10%) of materials,such as adhesives, waxes, oils and the like.

Exemplary absorbent structures for use as the absorbent assemblies aredescribed in U.S. Pat. No. 4,610,678 (Weisman et al.); U.S. Pat. No.4,834,735 (Alemany et al.); U.S. Pat. No. 4,888,231 (Angstadt); U.S.Pat. No. 5,260,345 (DesMarais et al.); U.S. Pat. No. 5,387,207 (Dyer etal.); U.S. Pat. No. 5,397,316 (LaVon et al.); and U.S. Pat. No.5,625,222 (DesMarais et al.).

The absorbent article may further comprise at least one wetnessindicator which is visible from the exterior of the article and whichchanges appearance when contacted with a body exudates, in particularurine. The wetness indicator (not shown) may be placed, when seen fromthe exterior of the article, between the two channel-forming areas 226of FIG. 9, and/or between any of the channel-forming areas 226 and anyof the lateral edge or both. The wetness indicators of the presentinvention may be according to any wetness indicating system known in theart. It is known that wetness indicator can provide an appearing signal,a disappearing signal or a color change signal, and combinationsthereof. The wetness indicator may advantageously provide a color changesignal, which may be typically obtained by a composition having a firstcolor when dry and a second color different form the first color whenwet, both colors being discernible by an external observer consideringthe article in a dry and a wet state.

The wetness indicator may in particular be a color change compositioncomprising a suitable pH indicator or another chemical substance thatchanges color when contacted with urine. Such compositions are forexample disclosed in WO03/070138A2 or US2012/165771 (Ruman). Moregenerally, the wetness indicator compositions of the invention may be asdisclosed in WO2010/120705 (Klofta), comprising a colorant, a matrix anda stabilizer. The color change composition may be a hot-melt adhesive,which allows for an easy application of the composition on a substratecomponent of the article for example by a slot coating process orprinted adhesive coating as disclosed e.g. in US2011274834 (Brown). Thewetness indicator composition may be applied on any layer of theabsorbent article using a conventional technique, for example printing,spraying or coating, during the making of the absorbent article. Thelayer may advantageously be the inner surface of the backsheet or theouter surface of the bottom side of the core wrap. This allows thewetness indicator to be visible from the exterior of the article bytransparency through the backsheet while keeping the wetness indicatorcomposition within the article. The wetness indicator may in particularbe easily applied on a layer such a nonwoven or film by a slot-coatingprocess especially if the composition is can be applied as a hot-melt.

Channels

In some embodiments, the absorbent core may comprise channels, or areassubstantially free of absorbent polymer particles or absorbent polymermaterial. The channels may provide improved liquid transport, and hencefaster acquisition, and more efficient liquid absorbency over the wholeabsorbent structure, in addition to reducing the stiffness of partiallyor fully loaded cores.

As shown in FIG. 9, the absorbent structure 213 comprises a firstsubstrate (a supporting sheet) 216, and an absorbent layer 217 ofabsorbent material 250. The absorbent material 250 comprises at least asuperabsorbent polymer material (absorbent particulate polymer material)and optionally a cellulosic material, such as a cellulose, e.g. pulp, ormodified cellulose in a absorbent particulate polymer material area.

The absorbent structure 213 also comprises one or more thermoplasticcompositions, as described above. The absorbent layer 217 is threedimensional and comprises a first substantially longitudinal channel 226and a second substantially longitudinal channel 226 that aresubstantially free of said superabsorbent polymer material. Othermaterials may be present in said channels 226, as further describedbelow, for example said one or more thermoplastic compositions and/or afiberized net structure 240.

The absorbent structure 213 and the absorbent layer 217 each have alongitudinal dimension and average length L, e.g. extending in thelongitudinal dimension of the structure or layer and a transversedimension and average width W, e.g. extending in the transversedimension of the structure or layer. The absorbent structure 213 and theabsorbent layer 217 each have a front region, being in use towards thefront of the user, back region, being in use towards the back of theuser, and therein between a crotch region, each extending the fulltransverse width of the structure/layer, and each having ⅓ of theaverage length of the structure/layer.

The absorbent structure 213 and the absorbent layer 217 each have a pairof opposing longitudinal side edges 218 extending in the longitudinaldimension of the structure or layer and a pair of opposing transverseedges 219, e.g. front transverse edge being in use towards the front ofa user (wearer), and a back transverse edge being in use towards theback of a user.

The absorbent layer 217 comprises at least a first channel 226 andsecond channel 226 that are substantially free of (e.g. free of) saidsuperabsorbent polymer particles, said channels 226 extending throughthe thickness height of the absorbent layer 217. By “substantially free”it is meant that in each of these areas the basis weight of theabsorbent material is at least less than 25%, in particular less than20%, less than 10%, of the average basis weight of the absorbentmaterial in the rest of the absorbent material deposition area of thecore. In particular there can be no absorbent material in these areas226. (It should be understood that, accidentally, a small, negligibleamount of superabsorbent polymer particles may be present in thechannel, which does not contribute to the overall functionality). Whenthe absorbent layer 217 comprises cellulosic or cellulose, in someembodiments the said first and second channels 226 are also free of suchcellulosic/cellulose material.

The first and second channel 226 each extend substantiallylongitudinally, which means typically that each channel 226 extends morein the longitudinal dimension than in the transverse dimension, andtypically at least twice as much in the longitudinal dimension than inthe transverse dimension.

Thus, this includes channels 226 that are completely longitudinal andparallel to the longitudinal direction of said absorbent layer 217; andthis includes channels 226 that may curve, provided the radius ofcurvature is typically at least equal (optionally at least 1.5 or atleast 2.0 times this average transverse dimension) to the averagetransverse dimension of the absorbent layer; and this includes channels226 that are straight but under an angle of (e.g. from 5°) up to 30°, orfor example up to 20°, or up to 10° with a line parallel to thelongitudinal axis. In some embodiments, there may be no completely orsubstantially transverse channels present in at least said crotchregion, or no such channels at all. Further descriptions of channels,including various dimensions and arrangements, are described in U.S.patent application Ser. Nos. 13/491,642, 13/491,643, 13/491,644, and13/491,648.

The channels 226 may typically be so-called “permanent” channels 226. Bypermanent, it is meant that the integrity of the channels 226 is atleast partially maintained both in the dry state and in the wet state,including during friction by the wearer thereon.

Permanent channels 226 may be obtained by provision of one or morethermoplastic compositions that immobilize said absorbent material 250,and/or said channels 226, e.g. or said absorbent layer 217, and/or thatimmobilize said supporting sheet 216 into said channels 226, or partthereof. As shown in FIG. 10, the absorbent core 207 may comprise inparticular permanent channels formed by bonding of a first supportingsheet or first substrate 216 and a second supporting sheet or secondsubstrate 216′ through the channels. Typically, glue may be used to bondboth supporting sheets throughout the channel, but it is possible tobond via other known means, for example ultrasonic bonding, or heatbonding. The supporting layers can be continuously bonded orintermittently bonded along the channels.

Such channels provide for fast liquid acquisition which reduces risk ofleakages. The permanent channels help to avoid saturation of theabsorbent layer in the region of fluid discharge (such saturationincreases the risk of leakages). Furthermore, whilst decreasing theoverall amount of superabsorbent polymer material in the absorbentstructure is reduced (by providing channels free of such material), thefluid handling properties of the absorbent structure, or diaper, areimproved. Permanent channels also have the further advantage that in thewet state the absorbent material is more restricted to move within thecore and remains in its intended application area, thus providing betterfit and fluid absorption. This can be demonstrated by comparing theamount of AGM loss in a wet state according to the WAIIT test for a corehaving two absorbent layers with permanent channels relative to asimilar core with the same amount of AGM and glue but having nochannels.

In short, the WAIIT test determines the amount of non-immobilizedabsorbent particulate material amount in the cores in wet conditions.Further information regarding the test can be found in US 2008/0312622A1. A permanent channel according to the disclosure has a percentage ofintegrity of at least 20%, or 30%, or 40%, or 50%, or 60, or 70%, or80%, or 90% following this test.

One or more thermoplastic composition(s) 240 (fiberized net structureand/or a hot melt adhesive) may be present between said supporting sheet216 and said absorbent layer 217, or parts thereof. For example, anadhesive material may be applied to portions of said supporting sheet216 that are to coincide with the channels 226, so that in said channelsthe supporting sheet can be bonded with said adhesive to the walls ofthe channel, or part thereof or to a further material; and/or theadhesive may be applied to portions of the supporting sheet 216 that areto coincide with the absorbent material 250, to immobilize said materialand avoid extensive migration thereof into said channels; the adhesivemay be applied over substantially the whole surface area of thesupporting sheet 216, e.g. substantially continuously and/orhomogeneously. This may for example be a thermoplastic hotmelt adhesiveapplied by printing, slot coating or spraying.

In addition, or alternatively, the absorbent structure may comprise oneor more adhesive materials applied on said absorbent layer or partthereof, that is already supported by said supporting sheet, (hereinreferred to as “first adhesive material”) e.g. after said absorbentmaterial is combined with/deposited on said supporting sheet to form anabsorbent layer. This may for example be a thermoplastic fibrousadhesive. In some embodiments, this may be applied continuously over theabsorbent layer, hence over the absorbent material and in the channels,to immobilize the absorbent layer and to optionally also adhere thesupporting sheet in said channel, as described above.

It should be understood that the first and second adhesive material maybe the same or different type of adhesive, for example as athermoplastic hotmelt adhesive.

In some embodiments, said one or more adhesive material are at leastpresent in the channels, for example at least said first adhesivematerial, or both said first and second adhesive material. It may thusbe present on the longitudinal walls of the channels (extending theheight of the absorbent layer and the length thereof). If the supportingsheet material folds into said channels, or part thereof, e.g. thesupporting sheet has undulations into said channels or part thereof,said undulations may be fixed to said walls or part thereof, to ensurethe channels are maintained (at least partially) during use.

The absorbent structure may comprise two or more than two channels, forexample at least 4, or at least 5 or at least 6. Some or all of thesemay be substantially parallel to one another, for example being allstraight and completely longitudinally, and/or two or more or all may bemirror images of one another in the longitudinal axis, or two or moremay be curved or angled and for example mirror images of one another inthe longitudinal axis, and two or more may be differently curved orstraight, and for example mirror images of one another in thelongitudinal axis.

The absorbent structure typically comprises one or more furthermaterial(s) (e.g. a second substrate) to cover the absorbent layer,herein referred to as a second substrate; for the avoidance of anydoubt, this is not a layer consisting of an adhesive material, howeverthe second substrate may be a layer comprising adhesive, for example onthe surface that is to contact the absorbent layer of the absorbentstructure. Thus, the second substrate may comprise on the surface to beplaced adjacent said absorbent layer of the absorbent structure, anadhesive material. The resulting structure is herein referred to as“absorbent core 207”.

This second substrate may be a further absorbent structure, with asecond absorbent layer and a second supporting sheet 216′, so that bothabsorbent layers are sandwiched between said supporting sheets 216;216′. The second absorbent structure may be identical to the firstabsorbent structure, or they may both be absorbent structure withchannels 226; 226′, but they may be different, for example havingdifferent channels, different number of channels, different adhesive,different adhesive application or combinations thereof.

In some embodiments, the second substrate may be a part of thesupporting sheet 216, which is folded over the absorbent layer 217 andthen sealed along the peripheral edges, to enclose the absorbent layer217.

In some embodiments, the further substrate is a further supportingsheet, i.e. the absorbent structure 213 is covered with a furthersupporting sheet 216′, said absorbent layer then being sandwichedbetween the two supporting sheets.

The supporting sheet of the first structure and/or the second supportingsheet of the acquisition material layer may fold into the channels ofthe first absorbent structure and/or optionally into the channels of theacquisition material layer, if present, or part of these channels. Theone or more adhesive material(s) may be at least present in thechannels, or part thereof, and the supporting sheets may be adhered toone another in said channels by one or more of these adhesivematerial(s). Another second adhesive may be present between the secondsupporting sheet and the acquisition material layer. Another adhesive(not represented) may be placed between the acquisition material layerand the absorbent layer, in addition to the thermoplastic composition240, to improve better adhesion of both layers.

In any of these cases, the second substrate can then be sealed to thesupporting sheet along the peripheral edges thereof, to enclose theabsorbent layer(s).

In any of these cases the supporting sheet or acquisition layer/sheetmay fold into (i.e. undulate into) said channels or part thereof, asshown in FIG. 10.

It may be adhered to the supporting sheet of the absorbent structure ofthe disclosure in said channels, e.g. by an adhesive material, asdescribed herein, ie., the substrate 216 (nonwoven dusting layer orsecond substrate) may be laminated to substrate 216′ (core cover orfirst substrate) or visa versa. Alternatively, or in addition, it may beadhered to the walls of the channels or part thereof.

In some embodiments the absorbent structure comprises such a furthermaterial overlaying said absorbent layer, and a pressure means isapplied selectively to said supporting sheet and/or to said furthermaterial, in those parts that coincide with said channels, to pressurizesaid supporting sheet and/or said further material into said channels ofthe absorbent structure and/or into the channels of a further (second)absorbent structure if present, to aid formulation of said undulationsand/or to aid adhering of the further material and said supporting sheetto one another in said channel, if an adhesive material is present asdescribed herein.

Further various embodiments of channels in an absorbent structure orcore may be found in U.S. Ser. No. 13/491,642. Processes for makingabsorbent cores with channels may be such as those described in U.S.Ser. Nos. 14/615,467 and 14/615,456.

In one of the embodiment herein, the supporting sheet 216 hasundulations that fold (undulate) into said first and second channels226, and optionally in to said further channel(s), of part thereof. Forexample the undulations may extend over about the full longitudinaldimension of the channel; they may for example extend to completeaverage height of the absorbent layer 217/channel, or for example onlyup to 75% thereof, or up to 50% of the average height of the absorbentlayer 217/channel. This aids immobilization of the absorbent material250 adjacent said channels 226 and said channels 226 of said layers.

The undulations may be adhered with said one or more adhesive material,e.g. said second adhesive material, to said walls of said channels 226.The supporting sheet 216 may alternatively, or in addition, be adheredin said channels 226 to said further material, e.g. second supportingsheet 216, describe herein above, e.g. with said first and/or secondadhesive.

The absorbent structure may comprise one or more adhesive material. Insome embodiments, it comprises a first adhesive material and/or a secondadhesive material, as described above, and in the manner describedabove.

The absorbent core herein may comprise a further second absorbentstructure that may comprise one or more adhesive materials.

Absorbent Material

The absorbent layer 217 comprises absorbent material 250, 66, and 74,that comprises superabsorbent polymer material (e.g. particles),optionally combined with cellulosic material (including for examplecellulose, comminuted wood pulp in the form of fibers). The furthermaterial described above (e.g. a further, second absorbent structure(not represented) may include an absorbent material, and the followingmay apply thereto too.

In some embodiment, the absorbent material 250 may comprise at least60%, or at least 70% by weight of superabsorbent polymer material, andat the most 40% or at the most 30% of cellulosic material.

In some other embodiments, the absorbent layer 217 comprises absorbentmaterial 250 that consists substantially of absorbent polymer material,e.g. particles, e.g. less than 5% by weight (of the absorbent material250) of cellulosic material is present; and said absorbent layer217/absorbent structure 213, may be free of cellulosic material.

Typically, the superabsorbent polymer material is in the form ofparticles. Suitable for use in the absorbent layer 217 can comprise anysuperabsorbent polymer particles known from superabsorbent literature,for example such as described in Modern Superabsorbent PolymerTechnology, F. L. Buchholz, A. T. Graham, Wiley 1998. The absorbentpolymer particles may be spherical, spherical-like or irregular shapedparticles, such as Vienna-sausage shaped particles, or ellipsoid shapedparticles of the kind typically obtained from inverse phase suspensionpolymerizations. The particles can also be optionally agglomerated atleast to some extent to form larger irregular particles.

In some embodiments herein, the absorbent material 250 as a whole and/orsaid particulate superabsorbent polymer material at least, has a highsorption capacity, e.g. having a CRC of for example at least 20 g/g, orat 30 g/g. Upper limits may for example be up to 150 g/g, or up to 100g/g.

In some embodiments herein, the absorbent material 250 comprising orconsisting of superabsorbent polymer particles that are formed frompolyacrylic acid polymers/polyacrylate polymers, for example having aneutralization degree of from 60% to 90%, or about 75%, having forexample sodium counter ions.

The superabsorbent polymer may be polyacrylates and polyacrylic acidpolymers that are internally and/or surface cross-linked. Suitablematerial are described in the PCT Patent Application WO 07/047598 or forexample WO 07/046052 or for example WO2009/155265 and WO2009/155264. Insome embodiments, suitable superabsorbent polymer particles may beobtained by current state of the art production processes as is moreparticularly as described in WO 2006/083584. The superabsorbent polymersmay be internally cross-linked, i.e. the polymerization is carried outin the presence of compounds having two or more polymerizable groupswhich can be free-radically copolymerized into the polymer network.Useful crosslinkers include for example ethylene glycol dimethacrylate,diethylene glycol diacrylate, allyl methacrylate, trimethylolpropanetriacrylate, triallylamine, tetraallyloxyethane as described in EP-A 530438, di- and triacrylates as described in EP-A 547 847, EP-A 559 476,EP-A 632 068, WO 93/21237, WO 03/104299, WO 03/104300, WO 03/104301 andin DE-A 103 31 450, mixed acrylates which, as well as acrylate groups,include further ethylenically unsaturated groups, as described in DE-A103 31 456 and DE-A 103 55 401, or crosslinker mixtures as described forexample in DE-A 195 43 368, DE-A 196 46 484, WO 90/15830 and WO 02/32962as well as cross-linkers described in WO2009/155265. The superabsorbentpolymer particles may be externally surface cross-linked, or: postcross-linked). Useful post-crosslinkers include compounds including twoor more groups capable of forming covalent bonds with the carboxylategroups of the polymers. Useful compounds include for example alkoxysilylcompounds, polyaziridines, polyamines, polyamidoamines, di- orpolyglycidyl compounds as described in EP-A 083 022, EP-A 543 303 andEP-A 937 736, polyhydric alcohols as described in DE-C 33 14 019, cycliccarbonates as described in DE-A 40 20 780, 2-oxazolidone and itsderivatives, such as N-(2-hydroxyethyl)-2-oxazolidone as described inDE-A 198 07 502, bis- and poly-2-oxazolidones as described in DE-A 19807 992, 2-oxotetrahydro-1,3-oxazine and its derivatives as described inDE-A 198 54 573, N-acyl-2-oxazolidones as described in DE-A 198 54 574,cyclic ureas as described in DE-A 102 04 937, bicyclic amide acetals asdescribed in DE-A 103 34 584, oxetane and cyclic ureas as described inEP-A 1 199 327 and morpholine-2,3-dione and its derivatives as describedin WO 03/031482.

The superabsorbent polymers or particles thereof may have surfacemodifications, such as being coated or partially coated with a coatingagent. Examples of coated absorbent polymer particles are disclosed inWO2009/155265. The coating agent may be such that it renders theabsorbent polymer particles more hydrophilic. For example, it may behydrophilic (for example, fumed) silica, such as Aerosils. The coatingagent may be a polymer, such as an elastic polymer or a film-formingpolymer or an elastic film-forming polymer, which forms an elastomeric(elastic) film coating on the particle. The coating may be a homogeneousand/or uniform coating on the surface of the absorbent polymerparticles. The coating agent may be applied at a level of from 0.1% to5%.

The superabsorbent polymer particles may have a particle sizes in therange from 45 μm to 4000 μm, more specifically a particle sizedistribution within the range of from 45 μm to about 2000 μm, or fromabout 100 μm to about 1000 or to 850 μm. The particle size distributionof a material in particulate form can be determined as it is known inthe art, for example by means of dry sieve analysis (EDANA 420.02“Particle Size distribution).

In some embodiments herein, the superabsorbent material is in the formof particles with a mass medium particle size up to 2 mm, or between 50microns and 2 mm or to 1 mm, or from 100 or 200 or 300 or 400 or 500 μm,or to 1000 or to 800 or to 700 μm; as can for example be measured by themethod set out in for example EP-A-0691133. In some embodiments of thedisclosure, the superabsorbent polymer material is in the form ofparticles whereof at least 80% by weight are particles of a size between50 μm and 1200 μm and having a mass median particle size between any ofthe range combinations above. In addition, or in another embodiment ofthe disclosure, said particles are essentially spherical. In yet anotheror additional embodiment of the disclosure the superabsorbent polymermaterial has a relatively narrow range of particle sizes, e.g. with themajority (e.g. at least 80%, at least 90% or even at least 95% byweight) of particles having a particle size between 50 μm and 1000 μm,between 100 μm and 800 μm, between 200 μm and 600 μm.

TABLE 1 option Unit 1 2 3 4 5 6 7 Fiberized net structure PO1 PO1 PO1PO1 PO2 PO5 PO1 composition Auxiliary adhesive PO1 PO1 PO1 PO3 PO2 PO5PO1 Total weight of [g/m²] 4/3 = 7 4/3 = 7 4/3 = 7 4/3 = 7 4/3 = 7 4/3 =7 2/2 = 4 fiberized net structure composition First substrate/Secondsubstrate Total weight of [g/m²] 15 9 7 15 15 15 12 fiberized netstructure composition + auxiliary adhesive Total weight of front [g/m²]35 19 12 35 35 35 32 or back end seal adhesive Wet immobilization Roomtemperature, [%] 27 27 25 29 50 51 27 initial 60 C/6 hour aged [%] 35 3234 30 31 48 41 Core end seal hang times Back end seal/Front end sealNormalized initial core [min] 1717/3327 434/864 25/138 166/109 1172/1172539/1162 1526/1342 end seal hang time >480 >60 <200 <200 >720 >480 >720(initial ~2 hrs after production at room temperature) Normalized finalcore [min] 1346*/1346* 770/421 30/64 215/157 1315/1069 1256/12561285/1285 end seal hang time >480 >250 <100 <200 >720 >480 >720(Final-60 C/6 hour aged) Normalized core end [min] 1020*/1020* 996/1002N/A (not 494/355 N/A N/A N/A seal hang time at >720 >480 available) >25050 C/2 weeks aged Channel hang times [min] (2 channels; left/right)Normalized initial [min] 1449/1057 1008/1321 645/750 294/306 1020/10201377/1377 1738/1738 channel hang time >480 >70 >70 <300 >480 >720 >720(initial ~2 hrs after production at room temperature) Normalized final[min] 997*/997* 974*/974 848/954 482/583 1119/1119 1172/1172 1199/1199channel hang time >800 >800 >500 <500 >800 >800 >1000 (final-60 C/6hours aged) Normalized channel [min] 1002/1002 1243/1377* 1354/1409*908/908 N/A N/A N/A hang time at 50 C/2 >1000 >1000 >600 >600 weeks agedWet normalized initial [min] 1119*/1119* N/A 1082/857 1136/628 952/952952/952 941/941 channel hang time >1000 >600 >1000 >600 >900 >900 *Testaborted

In table 1, absorbent cores or structures were made as described herein,using 10 gsm hydrophilic nonwoven core cover material (first substrate)and a 10 gsm hydrophobic nonwoven dusting layer (second substrate), andabsorbent material as described herein. Core adhesives and/or fiberizednet structures used may be a polyolefin-based material as describedherein. For example, it may be H.B. Fuller NW1414 (PO1), or may bepolypropylene-based, a blend of polyolefin polymers compounded with oneor more hydrocarbon tackifying resins and plasticizers (PO2 or PO5), ormaterials such as Henkel DM3800 (PO3). The table displays the wetimmobilization of each core (initial and aged), the core end seal hangtimes, and channel hang times (dry and wet), using the test methodsdescribed herein.

The normalized initial core end seal hang time of the present inventionmay be at least about 60 minutes, in some cases at least about 480minutes, at least about 600 minutes, or at least about 720 minutes. Thenormalized final core end seal hang time may be at least about 250minutes, in some cases at least about 480 minutes, or at least about 720minutes. The normalized initial channel hang time may be at least about70 minutes, in some cases at least about 480 minutes, or at least about720 minutes. The normalized final channel hang time may be at leastabout 800 minutes, in some case at least about 1000 minutes. A channelhang time of at least about 480 minutes may be considered a permanentchannel bond.

TABLE 2 G′, viscosity and ring & ball softening point data Viscosity @ T= 163° C. [mPas], spindel 27, 20 rpm; 20 min preheating, 10 min DMA DMADMA DMA stirring G′ G′ G′ G′ OR Tg in [Pa] [Pa] [Pa] [Pa] Viscosity**Viscosity @ [° C.] Temperature Temperature Temperature Temperature @ T= 150° C. [mPas], Ring & (Frequency 21° C. 35° C. 60° C. 90° C. T =spindel 27, 20 rpm; Ball Glue 6.28 Frequency Frequency FrequencyFrequency 175° C. 20 min preheating, Softening Code rad/s) 6.28 rad/s6.28 rad/s 6.28 rad/s 6.28 rad/s [mPas] 10 min stirring [° C.] PO1 137.80 × 10⁶ 3.52 × 10⁶ 1.40 × 10⁶ 0.25 × 10⁶ 2,620 5000 109 PO4 N/A N/AN/A N/A N/A 3,010 5700 109 PO3 2 5.24 × 10⁶ 2.85 × 10⁶ 1.02 × 10⁶ 0.21 ×10⁶ 3,500  7000** 81 PO2 5 6.35 × 10⁶ 3.33 × 10⁶ 0.94 × 10⁶   5 × 10³3,800 5500 82 PO5 6 3.63 × 10⁶ 1.86 × 10⁶ 0.55 × 10⁶ 1.41 × 10⁴ 4,6006700 84 PO6 N/A N/A N/A N/A N/A 2,500  3800** ~90

In Table 2, Storage Modulus G′ at 21° C. is reflected to describe thethermoplastic hotmelt properties of core adhesives and/or fiberized netstructures at lab measurement conditions of T=21° C. for PO1, PO2, PO5,and PO3 as described in table 1, as well as for PO4 and PO6, which arepolyolefin-based core adhesives and/or fiberized net structures, asdescribed herein. Storage Modulus G′ at 35° C. is reflected to describethe thermoplastic hotmelt properties during hygiene product usage, andStorage Modulus G′ at 60° C. and 90° C. are reflected to describe thethermoplastic hotmelt properties during hygiene product storageconditions, i.e. environment of global climate zones or transportation.

Thermoplastic compositions with a G′ at 21° C. and 6.28 rad/s greaterthan about 1.2×10⁶ Pa will likely have a high G′ at higher temperatures,such as 60° C. and/or 90° C. up to the melting point. These high G′levels at higher temperatures present processing challenges in contactand/or contactless applications, i.e. slot coating, summit, curtaincoater, spiral, omega, etc., due to, for example, higher viscosities.However, if these thermoplastic compositions, such as thermoplasticadhesive materials, properly wet and penetrate into the primary andsecondary substrates, they can create mechanical bonding via a greaterthan 300° or even 360° flow around sufficient individual substratefibers, and build up their final internal molecule structure andstrength. They can yield strong bonds with exceptional bonding hangtimes.

The storage modulus measured at 60° C. and 90° C. may be a measure forthe form stability of the thermoplastic adhesive material at elevatedambient temperatures. This value is particularly important if theabsorbent product is used in a hot climate where the thermoplasticadhesive material would lose its integrity if the storage modulus G′ at60° C. and 90° C. is not sufficiently high.

Test Methods

1. Bonded Nonwovens Hang Time (Core End Seal and Channel Hang Time)

Purpose

Cores utilizing perimeter sealing of core contents to prevent the corematerials from migrating to contact babies' skin must have seals strongenough to withstand the swelling pressures of the core materials and thepressures exerted from baby. This method determines the strength of theseal by measuring how long the perimeter seal can withstand a constantlyapplied force.

[For Channel hang time only: The purpose of the printed channel specificNormalized Core Hang Time (=>Normalized Channel Core Hang Time=NChHT) isto determine the bond strength of the AGM free channels. The bondstrength of printed AGM free channels in AFF (air felt free or cellulosefree) laminates has an impact on diaper performance as a too weakbonding might result in inferior core integrity and less wet fit. Thismethod determines the strength of the substrate to substrate bond bymeasuring how long the bonding is able to withstand a constantly appliedforce (static peel force).

Scope

Applicable for all diapers or absorbent cores having fully encapsulatedcores with a core endflap (core front and back end seals). Diapers orcores may be air felt free. Core may have AGM free channels. Channelspecific Normalized Core Hang Time (or Normalized channel hang time,NChHT) applicable for cores with AGM free channels showing the followingparameters: minimum distance between channels at the measuring point of10 mm and a minimum channel free distance at the measuring point of 20mm to the core bag edge to ensure a proper clamping of the nonwoven intothe clamps.

Equipment

-   -   Clips Medium Binder Clips 25 mm Capacity #72050. ACCO World        Product. Other suppliers: Yihai Products (#Y10003), Universal        Office Products (#10210), Diamond (#977114), or equivalent    -   Clips . . . Large Binder Clips 2 inch (50.8 mm). ACCO World        Product. Other suppliers: Yihai Products, Universal Office        Products, Diamond, or equivalent    -   Test Stand . . . RT-10 room temperature (Shear Tester) w/timer.        ChemInstruments, 510 Commercial Drive, Fairfield Ohio        45014-9797, USA; or equivalent. (See FIG. 1) Must be placed in a        vibration free area    -   Weight . . . Endseal: Normalized Core Hang Time (NCHT): 0.200 g        (+/−1 g) TW200 Shear Tester Weight with hook on top (to attach        to the clip). ChemInstruments, 510 Commercial Drive, Fairfield        Ohio 45014-9797, USA; or equivalent;    -   . . . Channel specific Normalized Core Hang Time (NChHT): 150 g        (+/−1 g) TW150 Shear Tester Weight with hook on top (to attach        to the clip). ChemInstruments, 510 Commercial Drive, Fairfield        Ohio 45014-9797, USA; or equivalent    -   . . . Cutting Tools Scissors and a 25.4 mm (1 inch) cutter        (convenient source, (see FIG. 2), e.g. JDC Precision Sample        Cutter made by Thwings-Albert Instrument Company Philadelphia        USA, cat#99, cut width 25.4 mm, accuracy at least +/−0.1 mm)    -   Metal . . . Ruler Traceable to NIST, DIN, JIS or other        comparable National Standard, graduated in mm, longer than the        length to be measured    -   Marker Permanent Fine-tip waterproof marker with no more than 2        mm pen width from convenient source    -   Sticks . . . Optional: Sticks from a convenient source, min.        length=sample with, stick weight <0.1 g    -   Temperature . . . Testo-temperature device (or equivalent) to        measure temperature at sample height.    -   Measurement . . . With an accuracy of ±0.5° C. and ±2.5% RH in        the range between −10° C. and +50° C.    -   Device . . . Testo GmbH & Co., Postbox 1140, D-79849 Lenzkirch        (www.testo.com) Article number for Testo 625: 0563 6251.

Sample preparation: For normalized initial core end seal hang time andnormalized initial channel hang time, test at room temperature about 2hours after production. For normalized final core end seal hang time andnormalized final channel hang time, test aged sample, meaning after 6hours at 60° C.

-   -   1. Open the diaper topsheet side up and place it flat onto a        table. For pull-ups open side seams and remove waistbands. Hold        the diaper with one hand and carefully remove Ears, Leg Elastics        and BLCs along the BLC continuous bond (outer edge) on both        Operator Side (OS) and Drive Side (DS) (see FIG. 3).    -   2. Gently remove topsheet and acquisition system without        damaging the core endflap gluing.

Back/Front Edge Bonding Specific Sample Preparation:

-   -   1. If the edge of the core encapsulation material is folded        under the core, unfold the endflap. If this is not possible        without tearing any core materials, discard the sample and pull        another sample.    -   2. The center of the core will be tested. Lay the pad onto the        25.4 mm cutter centered over the center of the core. Provide        sufficient length on the cutter to ensure sufficient length (at        least 65 mm) and cut the sample. Label the sample either        “UTE”/Front or “TE”/Back with the marker    -   3. After cut is made by the 25.4 mm cutter, use the scissors to        cut sample from the pad. Ensure that the sample measures 70        mm+/−5 mm. If the sample is too long, use scissors to cut off        the necessary amount of material at the open end of the sample        (area with core material). If the sample is too short, discard        the sample and pull another sample.    -   4. Put each sample under the UV-light to identify the AGM edge        and mark a line along the AGM edge at TE/Diaper Front and        UTE/Diaper Back.    -   5. Gently open samples like a book up to the marked line and        gently remove core material that is between Nonwoven Core Cover        (NWCC) and Nonwoven Dusting Layer (NWDL).    -   6. Optional Step: Use marker to mark the edge of glued area.        This should follow the shape of where the NWCC and NWDL are        glued together. (line may not be straight).

Side Seal Specific Sample Preparation:

-   -   1. Inspect the core side seal glue at Drive Side (DS) and        Operator Side (OS) for “open” areas, such as open channels,        because of missing glue, with free access to the core materials        (AGM)        -   a) If no open areas are present proceed with step 2.        -   b) In case of “open” areas skip further testing and report a            Failure.    -   2. Label the cut samples appropriate, e.g. DS.    -   3. Lay the pad on the 25.4 mm cutter approximately in the middle        of the crotch area. If you choose to cut and measure at a        different position, note down where, e.g. OS-TE or DS-UTE.    -   4. Cut the pad in cross machine direction with the 25.4 mm        cutter, use the scissors to cut sample in half    -   5. Optional: Measure the width of the sample at the gluing on        the NWCC side. The width has to be 25±2 mm.    -   6. Put each sample under the UV-light to identify the AGM edge        and mark a line along the AGM edge    -   7. Open samples like a book up to the marked inner line and        gently remove core material that is between Nonwoven Core Cover        and Nonwoven Dusting Layer.

Channel Specific Sample Preparation:

-   -   1. Label the cut samples appropriate, e.g. DS/OS        (driveside/operator side, or left/right)    -   2. Put each sample under the UV-light to identify the beginning        and the end of the channels in the front and in the back and        mark a line in cross direction.    -   3. Define the center of the channel area by using a ruler and        mark as the centerline.    -   4. Lay the pad on the 25.4 mm cutter and align to the centerline        cutting the sample out of the TE area.    -   5. Cut the pad in cross direction and optionally measure the        width of cut sample (target=25±2 mm).    -   6. Use the scissors to cut the sample that there are at least a        5 mm channel free flap at the inner side (cutting in machine        direction) to get an OS and a DS sample. All samples will be        tested/opened from the outside of the core.    -   7. Optional: Put each sample under the UV-light to identify the        channel AGM edge and mark a line along the AGM edges of the        channel.    -   8. Open samples from the outside of the core like a book up to        the beginning of the printed channel (respectively the first        marked line if you have marked it) and gently remove core        material that is between Nonwoven Core Cover and Nonwoven        Dusting Layer.

Test Procedure:

Set up the tester in an area where the temperature is constant andensure that the tester has at least 2 h time to reach the temperature ofthe environment. The same applies to the samples which usually will havethe same temperature as the environment and can then be measured rightaway. However if this is not the case one needs to wait at least 2 h toreach the temperature of the environment prior to the start of themeasurement.

-   -   1. The equipment may be operated between 17.5° C.-28.5° C. for        AFF products.    -   2. Roll the topsheet side part of the sample around a stick,        which is not heavier than 0.2 g (AGM to the inside) and staple        it for fixation. You may cut the stick with scissors if it is        longer than the sample width. The stick ensures that the samples        do not slip from the clamp.    -   3. Clamp the backsheet side/dusting layer side of the sample        strip into the jaw of the large binder clip hanging at the top        of the tester bar.    -   4. Clamp the other binder clip (medium) to the nonwoven core        cover.    -   5. Once all test samples have been prepared, (can setup multiple        tests at one time) begin picking up the weights from the tester        switch (this will begin the timer) and slowly attach the 200 g        weights for End flap or Side Seal or 150 g for AGM free channels        to the lower binder clips and lower slowly until the weights        hangs freely on the test strip.    -   6. As soon as the weight is released, push the timer reset        button for that sample to begin the timer at 0 minutes. NOTE:        The timer must be checked to ensure that it has begun counting        from 0.0 min. The operator should look for the number to change        from 0.0 min to 0.1 min.    -   7. Repeat procedure above for each sample prepared.    -   8. Measure and note down the temperature T_(a) of the tester        area at the sample height to the nearest 0.1° C. at the start of        the measurement. The allowed temperature range is 17.5°        C.-28.5° C. Measure the temperature at the beginning and at the        end of the measurement. T_(a) is the average temperature between        the two.    -   9. The timers will stop automatically once the sample weight has        fallen. This is the Hang time for that sample.

Calculation:

A) Temperature Adjustment to 23° C. (Normalization). Use the followingcalculation to adjust for temperatures

-   -   t23° C.: Corrected hang time in [min] at T=23 [° C.]    -   t_(a): actual hang time in [min] at the temperature T_(a)    -   T_(a): temperature [° C.] of the test equipment and the sample        during the measurement

The result actual hang time and the actual temperature are input oft_(a) and T_(a) using the above equation t_(23° C.).

Reporting:

Measure and Write Down the Following Values:

-   -   The actual temperature T_(a) to the nearest 0.1° C.    -   The actual hang time t_(a) to the nearest 0.1 min    -   The transformed hang time (t23° C.) to the nearest 0.1        (normalized hang time).

Wet normalized initial channel hang time is calculated by the normalizedinitial channel hang time test method, except sample is first dipped in200 ml 0.9% NaCl @ T=21° C. for 30 minutes and then tested.

2. Dynamic Mechanical Analysis (DMA) to Determine G′ for ThermoplasticCompositions

Temperature Sweep—Principle

A dynamic mechanical analysis (DMA) is done. An oscillatory shear stressis continuously applied to the adhesive resulting in an oscillatorystrain at constant amplitude, which is small enough to ensure fullyrecoverable deformation, whereas the temperature is increased (ordecreased) in discrete steps. The relationship between the sinusoidalstress applied and the resulting strain response as well as the shiftbetween both measures on the time axis are measured. The results arequantified by Storage Modulus [G′], Loss Modulus [G″] and Loss Factor[tan δ] of the adhesive in dependence of temperature.

Instrument:

TA Instruments DHR-3

Procedure:

-   -   1. Use a rheometer with 20 mm plate/plate geometry consisting of        an upper steel plate (diameter: 20 mm) and a lower peltier or        heating plate enabling temperature control. The rheometer needs        to be capable of applying temperatures from 0° C. to 150° C.    -   2. Calibrate Rheometer according to instrument manual.    -   3. Cut off and weigh a piece of adhesive of 0.37 g+/−0.01 g and        place it onto the centre of the Peltier or heating plate of the        rheometer and set the temperature to 150° C.    -   4. After the adhesive is molten, slowly lower the upper plate to        the geometry gap of 1000 micrometer. The velocity of the        rheometer head must not exceed 1000 micrometer per second in        order to achieve good contact between the adhesive and the upper        plate without damaging the adhesive sample.    -   5. Cover the geometry with the geometry cover for 2 minutes so        that the upper plate can heat up and the adhesive gets        completely molten.    -   6. Remove the cover and rotate the upper plate manually to        distribute the adhesive evenly between the upper plate and the        Peltier or heating plate and to ensure full contact of the        adhesive to the upper plate.    -   7. Afterwards cover the geometry with the geometry cover for        another 2 minutes.    -   8. Remove the geometry cover and check whether the adhesive is        distributed evenly.    -   9. Perform a pre-shearing at a shear rate of 2.5 seconds−1 for 1        minute to condition the adhesive.    -   10. After pre-shearing keep the temperature at 150° C. for 1        minute to let the adhesive settle and recover from pre-shearing.    -   11. Set Axial force control to 0.0 N with a sensitivity +/−0.1 N    -   12. Cool down to 25° C. and wait for 1 hour    -   13. Cool down to 10° C. and wait for 10 minutes    -   14. Start Temperature Sweep from 10 to 110° C. with temperature        step of 2° C.        -   Equilibrate at each temperature step for 60 s.        -   Strain Amplitude: 0.03%        -   Angular frequency: 6.28319 rad/s            Calculation/Reporting            From the temperature sweep report the following parameters:    -   Glass transition temperature in ° C.    -   (The glass transition temperature is defined at the peak maximum        of the tan δ value    -   Cross-over temperature in ° C.    -   (The cross-over-temperature is found at the end of the        rubber-plateau towards higher temperatures indicating the        beginning of the terminal zone. At the cross-over-temperature        storage- and loss modulus equal and tan δ value is 1)    -   Storage modulus at 21° C., 35° C., 60° C. and 90° C. in Pascal.        3. Wet Immobilization Test        Equipment    -   Graduated Cylinder    -   Stop watch (±0.1 sec)    -   Scissors    -   Light Box    -   Pen    -   Test solution: 0.90% saline solution at 23+/−2° C.    -   Metal ruler traceable to NIST, DIN, JIS or other comparable        National Standard    -   PVC/metal dishes with a flat surface inside and a minimum length        of the core bag length (n) to be measured and a maximum length        n+30 mm, width of 105±5 mm, height of 30-80 mm or equivalent    -   Electronic Force Gauge (Range 0 to 50 Kg)    -   Wet Immobilization Impact Tester Equipment (WAIIT), Design        package number: BM-00112.59500-R01 available from T.M.G.        Technisches Buero Manfred Gruna        Facilities:        Standard laboratory conditions, temperature: 23° C.±2° C.,        relative humidity: <55%        Sample Preparation    -   1. Open the product, topsheet side up.    -   2. Unfold the diaper and cut the cuff elastics approximately        every 2.5 cm to avoid chassis tension.    -   3. For pull-up products open the side seams and remove the        waistbands.    -   4. Lay the core bag flat and rectangular topsheet side up onto        the light box surface without any folds.    -   5. Switch on the light box to clearly identify the absorbent        core outer edges.    -   6. With a ruler, draw a line at the front and back absorbent        core outer edges.    -   7. Measure the distance (A), between the two markers and divide        the value by 2, this will be calculated distance (B).    -   8. Measure the calculated distance (B) from front marker towards        the middle of the core bag and mark it. At this marker draw a        line in the cross direction.        Test Procedure        WAIIT Calibration:    -   1. Make sure that the sliding board is in the lower position.        Open the front door of the WAIIT tester and connect the force        gauge hook to the upper sample clamp of the WAIIT. Make sure        that the clamp is closed before connecting the spring-balance.    -   2. Use both hands on the spring-balance to lift continuously and        as slowly as possible up the sliding board towards the upper        position. Record the average value (m₁) during the execution to        the nearest 0.02 kg.    -   3. Guide down the sliding board as slowly as possible to the        lower position and record the average value (m₂) read off during        execution to the nearest 0.02 kg.    -   4. Calculate and report the delta of m₁-m₂ to the nearest 0.01        kg. If the delta is 0.6 kg±0.3 kg continue measurement.        Otherwise, an adjustment of the sliding board is necessary. Make        sure that the sliding board is in lower position and check the        sliding path for any contamination or damage. Check if the        position of the sliding board to the sliding path is correctly        adjusted by shaking the board. For easy gliding some clearance        is needed. If not present, readjust the system.        WAIIT Test Settings:    -   Drop height is 50 cm.    -   Diaper load (l_(D)) is 73% of the core capacity (cc);        l_(D)=0.73×cc.    -   Core capacity (cc) is calculated as: cc=m_(SAP)×SAP_(GV), where        m_(SAP) is the mass of superabsorbent polymer (SAP) present in        the diaper and SAP_(GV) is the free swelling capacity of the        superabsorbent polymer. Free swelling capacity of the        superabsorbent polymer is determined with the method described        in WO 2006/062258. The mass of the superabsorbent polymer        present in the diaper is the average mass present in ten        products.        Test Execution:    -   1. Reset the balance to zero (tare), put the dry core bag on the        balance, weigh and report it to the nearest 0.1 g.    -   2. Measure the appropriate volume Saline (0.9% NaCl in deionized        water) with the graduated cylinder.    -   3. Lay the core bag, topsheet side up, flat into the PVC dish.        Pour the saline evenly over the core bag.    -   4. Take the PVC dish and hold it slanting in different        directions, to allow any free liquid to be absorbed. Products        with poly-backsheet need to be turned after a minimum waiting        time of 2 minutes so that liquid under the backsheet can be        absorbed. Wait for 10 minutes (+/−1 minute) to allow all saline        to be absorbed. Some drops may retain in the PVC dish. Use only        the defined PVC/metal dish to guarantee homogenous liquid        distribution and less retained liquid.    -   5. Reset the balance to zero (tare), put the wet core bag on the        balance. Weigh and report it to the nearest 0.1 g. Fold the core        bag just once to make it fit on the balance. Check to see if the        wet core bag weight is out of limit (defined as “dry core bag        weight+diaper load±4 ml”). For example, 12 g dry core bag        weight+150 ml load=162 g wet core bag weight. If the actual wet        weight on the scale is between 158 g and 166 g, the pad can be        used for shaking. Otherwise scrap the pad and use the next one.    -   6. Take the loaded core bag and cut the pad along the marked        line in the cross direction.    -   7. Put the back of the wet core bag onto the balance (m₁). Weigh        and report it to the nearest 0.1 g.    -   8. Take the wet core and clamp the end seal side in the top        clamp of the sample holder of the WAIIT (open end of the core        oriented down). Next, clamp both sides of the core with the side        clamps of the sample holder making sure that the product is        fixed to the sample holder along the whole product length. Make        sure not to clamp the absorbent core, only the nonwoven; for        some products this means securing the product with only the        barrier leg cuff.    -   9. Lift up the sliding board to the upper position by using both        hands until the board is engaged.    -   10. Close the safety front door and release the slide blade.    -   11. Reset the balance to zero (tare), take the tested core bag        out of the WAIIT and put it on the balance (m₂). Report the        weight to the nearest 0.1 g.    -   12. Repeat steps 7 to 11 with front of the wet core bag.        Reporting:    -   1. Record the dry core bag weight to the nearest 0.1 g.    -   2. Record the wet weight before (m_(1 front/back)) and after        (m_(2 front/back)) testing, both to the nearest 0.1 g.    -   3. Calculate and report the average weight loss (Δm) to the        nearest 0.1 g: Δm=(m_(1front)+m_(1back))−(m_(2front)+m_(2back))    -   4. Calculate and report the weight loss in percent to the        nearest 1%, (Δm_(rel)):        (Δm_(rel))=(((m_(1front)+m_(1back))−(m_(2front)+m_(2back)))×100)/(m_(1front)+m_(1back))    -   5. Calculate and report Wet Immobilization (WI) as:        WI=100%−Δm_(rel)

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

We claim:
 1. An absorbent core extending in a lateral direction and alongitudinal direction, the absorbent core having a front edge, a backedge, and two side edges, the absorbent core comprising: a firstsubstrate and a second substrate, wherein each substrate comprises aninner surface and an outer surface, an absorbent material comprising anabsorbent particulate polymer disposed between the first substrate andthe second substrate in an absorbent particulate polymer material area,the absorbent particulate polymer material area encompassing one or morechannel area(s) that are substantially free of absorbent material, a hotmelt adhesive applied directly to the inner surface of at least one ofthe first or second substrate, wherein the adhesive bonds the innersurface of the first substrate to the inner surface of the secondsubstrate through the one or more channel area(s) substantially free ofabsorbent material; wherein the bond of the inner surface of the firstsubstrate to the inner surface of the second substrate through the oneor more channel area(s) substantially free of absorbent material has anormalized final channel hang time of at least 800 minutes, and whereinthe absorbent material is supported by and immobilized between the firstand second substrate layers by a fiberized net structure.
 2. Theabsorbent core of claim 1, wherein the absorbent core is substantiallycellulose-free.
 3. The absorbent core of claim 1, wherein the adhesiveis applied to the inner surface of the first or second substrate suchthat the first substrate and the second substrate are bonded along thefront edge and along the back edge of the absorbent core to create afront end seal and a back end seal.
 4. The absorbent core of claim 1,wherein the absorbent core comprises only one adhesive.
 5. The absorbentcore of claim 1, wherein the absorbent particulate polymer material areacomprises only one adhesive.
 6. The absorbent core of claim 1, whereinthe hot melt adhesive comprises at least one polyolefin.
 7. Theabsorbent core of claim 1, wherein the core comprises a second hot meltadhesive.
 8. The absorbent core of claim 1, wherein the fiberized netstructure is applied at an amount from about 2 to about 7 grams/m². 9.The absorbent core of claim 1, wherein the hot melt adhesive providesthe fiberized net structure.
 10. The absorbent core of claim 1, whereinthe total amount of adhesive and fiberized net structure is from about 2to about 15 grams/m² in the absorbent particulate polymer material area.11. The absorbent core of claim 1, wherein the amount of hot meltadhesive in the absorbent particulate polymer material area is fromabout 2 gsm to about 7 gsm.
 12. The absorbent core of claim 1, whereinthe amount of hot melt adhesive in the absorbent particulate polymermaterial area is from about 2 gsm to about 4 gsm.
 13. The absorbent coreof claim 1, wherein the fiberized net structure has an average fiberthickness of about 35 μm.
 14. The absorbent core of claim 1, wherein thefirst substrate is a nonwoven core cover and the second substrate is anonwoven dusting layer.
 15. An article comprising the absorbent core ofclaim
 1. 16. The article of claim 15, further comprising a topsheet anda backsheet, wherein the absorbent core is disposed between the topsheetand the backsheet.
 17. The absorbent core of claim 1, wherein the hotmelt adhesive has a storage modulus (G′ at 21° C. and 6.28 rad/s) ofgreater than 1.2×10⁶ Pa.
 18. The absorbent core of claim 3, wherein thenormalized final core end seal hang time is at least 480 minutes.
 19. Anabsorbent core extending in a lateral direction and a longitudinaldirection, the absorbent core having a front edge, a back edge, and twoside edges, the absorbent core comprising: a first substrate and asecond substrate, wherein each substrate comprises an inner surface andan outer surface, an absorbent material comprising an absorbentparticulate polymer disposed between the first substrate and the secondsubstrate in an absorbent particulate polymer material area, a hot meltadhesive applied directly to the inner surface of the first or thesecond substrate such that the first substrate and the second substrateare bonded along the front edge and along the back edge of the absorbentcore to create a front end seal and a back end seal; wherein the frontend seal and the back end seal each have a normalized final core endseal hang time of at least 250 minutes, and wherein the absorbentmaterial is supported by, and immobilized between the first and secondsubstrate layers by a fiberized net structure.
 20. The absorbent core ofclaim 19, wherein the absorbent core is substantially cellulose-free.21. The absorbent core of claim 19, wherein the absorbent core comprisesonly one adhesive.
 22. The absorbent core of claim 19, wherein theabsorbent core comprises a second hot melt adhesive.
 23. The absorbentcore of claim 19, wherein the hot melt adhesive provides the fiberizednet structure.
 24. The absorbent core of claim 19, wherein the fiberizednet structure has an average fiber thickness of about 30 μm.